o- I; 5! Ji ffi" -D ru m AN ACCOUNT OF THE CRUSTACEA OF NORWAY AN ACCOUNT OF THE CRUSTACEA OF NORWAY U'lTH SHOPxT DESCRIPTIONS AND FIGURES OF ALL THE SPECIES BY G. 0. SARS, PROFESSOR AT THE UNIVERSITY OF CHRISTIANIA VOL. II. ISOPODA BERGEN PUBLISHED BY THE BEEGEN MUSEUM SOLD BY ALB. CAMMEEMEYEES FORLAG, CHEISTIANIA 189! BERGEN. JOHN GRIEG PREFACE. I have now the satisfaction of presenting to the scientific world the 2nd Volume of my work on the Crustacea of Norway. The Isopoda have not yet been treated of as a whole by any of the Scandinavian zoologists, although of solitary groups there have recently been published several excellent monographs, especially by Danish zoologists. Thus the Cymothoidce and ^Egidce have been treated of by Prof. Liitken and Meinert, the Cirolanidce by Dr. Hansen, and the extensive group Oniscoida by Mr. Budde- Lund. In all these monographs, however, both indigenous and foreign forms are combined, and the present Volume is accordingly the first faunistic work on Scandinavian Isopoda. In as much as this is the case, I hope that it will be of practical use to future zoologists, who may enter upon a study of the indigenous Isopod-Fauna. The plan according to which the work has been carried out, is chiefly that followed in the 1st Volume treating of the nearly-allied order Amphipoda. Of course, in so doing, some limits have presented themselves, beyond which the treating of the several forms could not pass, though in some instances, perhaps, a more detailed account would havs been desirable. The difficulties connected with the elaboration of this work have been by no means small. I have especially taken great pains in investigating and critically determining the Epicarida, which undoubtedly is the most difficult of the Isopod groups, being at the same time of very prominent interest in biological respects. It is not improbable that some deficiencies and perhaps also errors may be found to exist in my account of this or the other groups ; but considering the great difficulties connected with this investigation, I hope that they will be excused, and that they will soon be corrected by other zoologists. I may add, that the account especi- ally of the Oniscoida and Epicarida would have been still much more defective, if I had not been assisted in a most ready manner by the directors of the VI Copenhagen Museum, who have kindly placed at my disposal the rich collections of these groups procured during recent years by that Museum. As to the systematic arrangement here adopted, some objections may perhaps be urged against its validity. I must, however, observe, that it is chiefly out of regard to the merely practical side of the question, that I have been induced to retain unaltered this arrangement, proposed by me several years ago, and now sanctioned by several distinguished authors. In the Appendix to the Volume, some additions, chiefly as regards the geographical distribution of the species, are given, as also descriptions and figures of a few new species. The plates, as in the 1st Volume, have been prepared by the autographic method, the appropriateness of which has been proved both by the plates of the 1st Volume, and by several other illustrations published by the present author. I am sorry, however, that some of the last plates of the present Volume have been less perfectly executed, owing to some want of care on the part of the lithographer in the transfer of my drawings. Yet I hope that these plates too will be found sufficiently distinct to allow of easily recognising the species illustrated. In concluding this short preface, I wish in the first place to express my most hearty feeling of gratitude to my friend, the distinguished Danish zoologist, Dr. Hansen, for the kindness with which he has at all times assisted me, both by forwarding to me specimens from the Copenhagen Museum, and by giving me much useful advice and information. I am likewise indebted to Mr. Budde- Lund, the well-known author of the work on air-breathing Isopoda, for identifying some difficult forms of Oniscoitla. There are also several other gentlemen to whom my thanks are due, partly for having sent me specimens, partly for having assisted me in other ways. Finally, I beg to offer my best thanks to the direction of the Bergen Museum for the readiness with which it has undertaken the continued publication of this great work. G. 0. Sar*. PRINCIPAL WORKS ON ISOPODA. 1 ) Isopoda in general. H. Milne-Edwards. Histoire naturelle des Crustaces, Tome III. 1840. H. Itathlce. Beitrage zur Fauna Norwegens. 1843. H. Kroyer. Crustacees, in Gaimard's Voyage en Scandinavie, etc. Atlas. 1849. J. Dana. Report on the Crustacea of the United States Exploring Expe- dition. Part II. 1853. P. v. Beneden. Recherches sur la faune littorale de Belgique. Crustaces. 1861. Cam. Heller. Carcinologische Beitrage zur Fauna des adriatischen Meeres. Isopoda. 1866. Sp. Bate & Westivood. A History of British sessile-eyed Crustacea. Vol. II. 1868. Fr. Meinert. Crustacea Isopoda, Amphipoda et Decapoda Danine. 1877. Crustacea malacostraca (Det videnskabelige Udbytte af ,,HauchV Togter). 1890. Oscar Haryer. Report on the marine Isopoda of New England and adjacent Waters. 1878. P. P. C. HoeJc. Die Crustaceen gesammelt wahrend der Fahrten des ,,Willem Barents". 1882. G. 0. Sars. Oversigt af Norges Crustaceer I. 1882. Crustacea of the Norwegian North Atlantic Expedition. 1885. Fr. Beddard. Report on the Isopoda of the Challenger Expedition. 1886. 1 ) It is of course not my intention to give here an} 7 complete account of the litera- ture referring to the Isopoda, as such an account would fill several sheets; it is only my pur- pose to record some of the more important works, especially those referring to the northern fauna. The works are, as a rule, enumerated in chronological succession, and besides those treating of the Isopoda in general, some particular Avorks are recorded for each of the chief groups, an arrangement which I hope may be of some practical use in facilitating reference. VIII H. J. Hansen. Oversigt af de paa Dijrnphna-Togtet indsamlede Krebsdyr. 1886. Oversigt over det vestlige G-r0nlands Fauna af malacostrake Havkrebsclyr. 1887. Isopoden, Cuinaceen und Stoinatopoden der Deutschen Plankton Expedition. 1895. D. Robertson. Catalogue of the Amphipoda and Isopoda of the Firth of Clyde. 1888. T. R. R. Stebbing. A History of Crustacea. Eecent Malacostraca. 1893. Jules Bonnier. Edriophthalmes (Resultats scientifiques de la campagne du ,,Cau- dan" dans le golfe de G-ascogne). 1896. Chelifera. H. Kroyer. Fritz Mutter. Nye Arter af Slsegten Tanais. Nat. Tidsskr. Bd. IV. 1842. Ueber der Bau der Scheerenasseln. Arch. f. Naturg. Jahrg. XXX, Bd. I. 1864. Bidrag til kiinnedomen om de inom Sverige och Norrige fore- kommande Crustaceer af Isopodernes underordning och Tanai- dernes faniilj. 1865. Zur Kenntniss von Bau und der Entwickelung von Tanais. Je- naische Zeitschrift, Bd. 3. 1870. Revision af Gruppen Isopoda chelifera. Arch. f. Mathem. & Naturvid. 1881. Middelhavets Saxisopoder. Arch. f. Math era. & Naturvid. 1886. Norman & Stebbing. On the Crustacea Isopoda of the ,,Lightning", ,,Porcupine" and Valorous" Expeditions. Apseudidse & Tanaidse. 1884. H. Blanc. Contribution a 1'histoire naturelle des Asellotes heteropodes. 1884. W. Lilljeborg. Anton Dohrn. G. 0. Sais. Chr. Liitken. E. Hesse. A. Dohrn. Flabellifera. Nogle Bemserkninger om de nordiske ^Egaarter. Vid. Medde- lelser. 1859. Tillseg til ,,Nogle Bemserkninger oin de nordiske JEga-Arter". Vid. Meddelelser. 1861. Memoire sur les Pranizes et les Ancees. 1864. Zur Kenntniss des Baues von Paranthura Costana (Untersuchun- gen tiber Bau und Entwickelung der Artliropoden). 1870, IX A. Dolirn. Entwickelung und Organisation von Praniza (Anceus) rnaxillaris. Ibid. J. Schodte & Fr. He-inert. Symbolse ad monographiam Cymothoarum. I. ^gidse. 1879. 0. Harger. Report on the result of dredging under the supervision of Alex. Agassis, on the east coast of the United States during the sum- mer of 1880. Isopoda. 1883. Norman & Steblriny. On the Crustacea of the ,,Lightning", ,,Porcupine" and ,,Valorous" Expeditions. Anthuridse. 1884. C. Bovall'ms. A new Isopod from the coast of Sweden. Bihang till Vetensk. Akad. Handl. Bd. 10. 1885. A new Isopod from the Swedish Arctic Expedition. Ibid. New or imperfectly known Isopoda. II. Ibid. Bd. 11. 1886. H. J. Hansen. Cirolanidse et families nonnullse propinqvse. 1890. Valvifera. H. Goodsir. On 2 new species of Leachia. Edinb. New. Ph. Journ. Vol. XXX. 1841. T. R. R. bteWmg. On a- new species of Arcturus (A. danmoniensis). Ann. Nat. Hist. 1874. E. J. Miers. Revision of the Idoteidse. 1881. Ch. Chilton. Revision of New Zealand Idoteidse. Trans. N. Z. Inst. 1889. A. Dolfuss. Les Idoteidse des cotes de France. Feuille des jeunes Natu- ralistes 1898. J. E. Benedict. The Arcturidse in the U. S. National Museum. Proc. of the biol. Soc. of Washington. 1898. Asellota. H. Kroyer. Munna, en ny Krebsdyrslsegt. Nat. Tidsskr. Bd. 2. 1839. M. Sars. Beskrivelse af en ny Slsegt og Art af Isopoder, Munnopsis typica Sars. Chr. Vid. Selsk. Forhandl. 1860. Gr. 0. Sars. Om en anomal Gruppe af Isopoder. Chr. Vid. Selsk. Forhandl. 1863. A. Dohrn. Die embryonale Entwickelung des Asellus aqvaticus. Zeitschr. f. wiss. Zoologie. 1866. X C. Bovattius. Notes on the family Asellidse. Bihang till Kgl. S. Vetensk. Hand!. Bd. II. 1886. C. G. Sye. Beitrag'e zur Anatomic und Histologie von Jaera marina (Inau- gural-Dissertation). 1887. Oniseoida. J. E. Brandt. Conspectus monographic Oniscodorum Latreillii. 1833. V. v. Eber. Helleria, eine neue Isopoden-Gattung aus der Familie der Onis- ciden. Verhandl. d. zool. botan. Gesellsch. in Wien. 1868. Max Weber. Ueber einige neue Isopoden der Niederlandischen Fauna. Tydschr. d. nederlandsche Dierk. Vereenigg. 1881. Anatomiscb.es iiber Trichonisciden. Arch. f. mikrosk. Anatomic. Bd. XIX. O. Budde-Lund. Crustacea Isopoda terrestria. 1885. R. F. Scharff. The Irish Wood-lice. 1894. Bopyrida. H. Kroyer. Bopyrus abdominalis. Nat. Tidsskr. Bd. 3. 1840. W. Lilljeborg. Les genres Liriope et Peltogaster. 1859. E. Hesse. Observations sur des Crustaces rares on nouvelles des cotes de France. Ann. scienc. nat. 1865. 1867, 1876. R. Buehholtz. Ueber Hemioniscus, eine neue G-attung parasitischen Isopoden. Zeitschr. wiss. Zool. Bd. 16. 1866. Fr. Mutter. Bruchstiicke zur Naturgeschichte der Bopyriden. Jen. Zeitschr. Bd. 6. 1871. R. Kossmann. Studien liber Bopyriden. Mittheil. a. d. zool. Station zu Neapel. 1881, and in Zeitschr. f. wiss. Zool. Bd. XXXV. Neueres tiber Cryptonisciden. Sitzungsb. d. Akad. d. Wissensch. zu Berlin. 1884. A. Giard & J. Bonnier. Contribution a 1'etude des Bopyriens. 1887. Sur les Epicarides de la famille des Dajidse. 1889. / Prodrome d'une Monographic des Epicarides du golfe de Naples 1890. / Sur les Epicarides parasites des Arthrostraces. Travaux du Labor, de Wimmereux-Ambleteuse. 1895. General Remarks, The present order being rather nearly allied to that of the Amphipoda, a similar terminology may on the whole be applied to both. The body, which in most cases exhibits a more or less depressed, not as in the Amphipoda com- pressed, form, admits of being divided into 3 chief sections, viz., cephalon, meso- some and metasome, the urosonie not being, as in the Amphipoda, defined as a particular division. In the group CheUfem, as also in the family Gnathudas among the FlabeUifera, the cephalon is coalesced with the 1st segment of the mesosome, for which reason, in the said forms, this section may more properly be termed cephalosome. As to the several appendages, those of the cephalon are the same as in the Amphipoda, and are denominated in a similar manner. The 2 pairs of antennae, it is true, are generally described as inner and outer, not as superior and inferior; but on a closer examination it may be easily proved, that in all forms the outer antennas in reality issue beneath the inner. The 2 pairs of maxilla?, in the typical Isopoda, differ somewhat from those in the Amphipoda, the anterior ones being generally devoid of palp, whereas the posterior ones carry outside the outer lobe a lamellar appendage which ought to be regarded as a palp. The maxillipeds only exhibit a single pair of masticatory lobes, answering to the basal lobes in the Amphipoda. On the other hand they are provided outside with a more or less distinctly developed epignath, wholly wanting in the Amphipoda. In parasitic forms, as usual, the oral parts become more or less modified in their struc- ture. The appendages of the mesosome, the legs, exhibit only in the terres- trial Isopoda (Oniscoidea) such a uniform appearance as to justify the name given to the order; but in by far the greater part of the Isopoda, the structure of the legs is rather diversified, in some cases (for instance in the Munnopsidee) even more so than in the Amphipoda. The 1st pair generally differ conspicuously from the next succeeding pnes, being prehensile and applied to the oral region, 1 Crustacea. thus meriting the name of true gnathopoda, but in some instances the 2 suc- ceeding pairs assume a similar prehensile nature (yEgidse, Cirolanida?, Idotheidse). In the group Chelifera, the 1st pair of legs attain their greatest development, exhibiting the character of true chelipeds, as in the higher Crustacea. The number of legs is 7 pairs, as in the Amphipoda, with the one exception of the family Gnathiidce, in which only 6 pairs are counted, the last pair being wholly absent. This, as is well known, is also the case with the young of all Isopoda, immedi- ately after being hatched. The coxal plates to which the legs are appended, are far from being so distinct in the Isopoda as in the Amphipoda. In a great number of forms not even a trace of these plates is to be seen, and, when present, they are always so rirmly connected with the corresponding segments, as scarcely to admit of being detached from them by dissection. In no case are branchial lamella? found to be appended to these plates. The appendages of the metasome are. as a rule, 6 pairs, as in the Amphipoda. Of these the 5 anterior ones are in some instances natatory in character. But in the greater part of the Isopoda their function has changed to be more or less ex- clusively respiratory, and in such cases they lie densely crowded beneath the shield- like terminal portion of the metasome. In the group Asellota the 1st pair of these appendages are, as a rule, peculiarly modified, being in the female coalesced to a single thin opercular plate, covering the succeeding pairs, whereas in the male they are transformed into complicated copulative organs. Only the last pair can properly be termed uropoda. Their structure is rather variable in different Isopoda. affording excellent systematic characters. The telson is distinctly defined only in the Anthuridce. In all other Isopoda it is fused with the preceding seg- ment, and in some cases all the segments of the metasome are coalesced to a single shield-like plate, the so-called urus. The systematic arrangement adopted in the present work is that pro- posed by the present author in 1882 (Oversigt af Norges Crustaceer I). I give below a Synopsis of the 6 Tribes into which the Isopoda, according to this ar- rangement, are divided, each tribe being defined by 3 characters, viz., those of the 1st pair of legs, the uropoda, and the pleopoda: Legs of 1st pair cheliform. distinctly Uropoda developed, terminal. Pleopoda, when! . J 1. Chelifera. exclusively natatory. not cheli- form. Uropoda lateral, Uropoda terminal. forming together with the terminal segment of the metasome a caudal fan. Pleopoda for the most part natatory. valve-like, inflexed, arching over the pleopoda, which to a great extent are bran- chial. Pleopoda exclusively bran- chial, generally covered by a thin opercular plate (the modified 1st pair.) 2. Flabellifera. Valvifera. 4. Asellota. Pleopoda fitted for air-) . | o. Omscoidea,, breathing. Pleopoda, when present, ex- clusively branchial in the adult animal, and not cov- ered by any operculum. 6. Epicarida. Tribe 1. CHELIFERA. Body generally slender, nearly cylindric in form. Cephalon and the 1st segment of mesosome coalesced, forming together a kind of carapace, which on each side contains a small branchial cavity. The 6 other segments of mesosome well defined, with the coxal plates small or inconspicuous. Metasome generally composed of 6 segments, the 5 anterior short, subequal, the last much the largest. Eyes distinct or wanting. Superior antennae generally simple, sometimes, however, provided with a distinct secondary appendage; inferior ones smaller than 'the superior and issuing immediately beneath them. Mandibles with or without palps. Anterior maxillae provided with a reflexed, setiferous palp; posterior ones very small, often quite rudimentary. Maxillipeds more or less coalesced at the base, and each having outside a membranous epignath projecting within the branchial cavity. 1st pair of legs very strong, curving anteriorly, and each terminating in a cheliform hand; 2nd pair sometimes unlike the succeeding ones, which are simple, ambulatory. Pleopocla, when present, comparatively small, natatory, rami lamelliform. Uropoda terminal, consisting of a short basal part and one or two terminal filaments. Sexual difference often very pronounced. Remarks. This is certainly a very anomalous group, differing, as it does, in certain particulars very markedly from the typical Isopoda, and exhibiting some points of resemblance to apparently widely distant crustacean orders, for instance the Cumacca. For this reason it lias been proposed by some authors to remove this group altogether from the Isopoda, and to regard it as a distinct order. I do not find, however, that such an arrangement affords any real ad- vantMgc. and as the present forms agree in many other respects with the Isopoda. I prefer to retain them within that order as an anomalous tribe. The most striking external feature is undoubtedly the peculiar modification of the 1st pair of legs, or the gnathopoda, into strong cheliform organs, a character not found in any other Isopoda, and somewhat recalling the higher Crustacea, crabs and lobsters. It is indeed from this character that the name of the group, chelifera, proposed by the author, has been derived. Another very anomalous feature is the complete fusion of the chephalon and the 1st segment of the mesosome, to form a kind of carapace, and the localisation of the respiration to that part, instead of. as in other Isopoda, to the metasome. In connection therewith is also the more anterior situation of the heart in the present forms. The group contains 2 distinct families, Apseudidce and Tanaidoe, both represented in the fauna of Norway. Fam. 1. Apseudidae. Body more or less elongated, tapering behind, and subdepressed in front, with the cephalosome rather broad and carinated laterally. Free segments of mesosome very sharply marked off, and exhibiting at the insertions of the legs, distinct, though small coxal plates. Metasome very narrow, composed of 6 well- defined segments. Eyes well-developed or rudimentary, being placed on distinctly defined lobes at the outer corners of the frontal margin. Superior antenna? is- suing far apart, just beneath the ocular lobes, and consisting of a Sarticulate peduncle and 2 unequal filiform flagella. Inferior antennse much smaller than the superior, and sometimes having at the end of the peduncle a small squami- f orm appendage. Mandibles rather strong, each with a well-developed molar expansion and a triarticulate palp. Anterior niaxilke with 2 masticatory lobes, palp biarticulate and terminating in a number of slender seise ; posterior ones normally developed, though rather small. Epignath of maxillipeds rather large, forming a broad vaulted plate, terminating in a digitiform point. The 2 anterior pairs of legs unlike, the others, and provided at the base with a small biarticulate exopodite; 1st pair distinctly cheliform and much Districted at the base, with the ischial joint obsolete; 2nd pair very powerful, fossorial in character, the outer joints being coniplanated and edged with strong spines. Pleopoda well developed and having the rami tipped with long natatory seise. Uropoda biramous, ranii filiform, multiarticulate, the inner one much the longer. Incubatory pouch normal. Remarks. - This family is well distinguished from that of the Tanaidce by the gradually tapering, and slightly depressed body, the greater development of the cephalosome, the peculiar structure of the antennse and of the 2nd pair of legs, and the presence of a rudimentary exopodite at the base of the 2 anterior pairs of legs. In the structure of the oral parts also, several well-marked differences are to be found. Thus the mandibles are provided with distinct palps, always wanting in the Tanaidce, and the maxillae are more fully developed, the anterior ones having 2 masticatory lobes, and the posterior ones exhibiting all the parts cha- racteristic of the typical Isopoda. Finally, the epignath of the rnaxillipeds is of an essentially different shape, and much more fully developed than in the Tanaidce. The family contains as yet 5 genera, viz., Apseudes Leach, Sphyrapus Norm. & Stebb., Parapseudes G. 0. Sars, Typhlapseudes Beddard, and Leiopus Beddard. Of these the 2 first-named genera are represented in the fauna of Norway. Gen. 1. ApSeudeS, Leach, 1814. Syn: Euplieus, Kisso. Rhoea, M. Edw. Generic Characters. - - Body, as a rule, very slender and attenuated, with the segments generally sharply marked off from each other. Cephalosome rather broad, depressed, more or less distinctly sculptured above, and generally terminating in front in a flattened rostral plate. First free segment of mesosome rather firmly connected to the cephalosome, and having the coxal plates spiniform, pointing obliquely in front. Metasome very narrow, more or less hairy, with the terminal segment rather produced. Ocular lobes generally well-defined, with or without distinct eyes. Superior antennae of similar structure in the two sexes, both flagella rather elongated. Inferior antennae furnished at the end of the peduncle outside with a scale-like setous appendage. Mandibles rather strong, cutting part divided into 2 superposed dentated lamellae and having behind a dense bunch of slender spines doubly or trebly forked at the tip, palp well developed and densely setous. Chelipeds in male larger than in female, with the hand more tumid and the thumb tuber- culated inside. Fossorial legs rather strongly built and of similar structure in the two sexes. All the pleopoda distinctly developed, rami uniarticulate and clothed with long ciliated setae. Uropoda with the ranii very slender, filiform, being composed of numerous short articulations. Remarks. This is the first recorded genus, and may therefore be regarded as the type of the family. It is chiefly characterised from>the next genus by the slender body, the flattened and distinctly sculptured cephalosome, the presence of a well-defined scale-like appendage to the inferior antennae, and the less pro- nounced sexual differences, as regards the superior antenna? and the first 2 pairs of legs. The genus contains several species from different parts of the Oceans, amounting to about 14 in all. Only a single species is as yet found off the coast of Norway. Apseudes spinosus, M. Bars. (PI. I & II.) BJtoea splnosa, M. Sars, Oversigt over de i den Norsk-arktiske Region forekominende Krebsdyr. Cbristiania Vid. Selsk. Forb. f. 1858, p. 30. Syn: Apseudes talpa, Lilljeb. (not Mont,). Specific Characters. - - Body very slender and elongated, gradually tapering behind. Cephalosome distinctly areolated above, with a slight notch on each side in front of the middle, rostral plate cordiform, defined on each side by a distinct notch, and terminating in an acute, somewhat deflexed point. Ocular lobes well- defined, outer part slightly tumefied, and armed anteriorly with a short pointed prominence. Free segments of inesosome defined by deep constrictions, and having the upper face slightly tubercular. 1st pair of coxal plates of moderate size, spiniform, and pointing obliquely outwards, the others rather small and rounded. Antero-lateral corners of the 5 posterior segments produced to triangularly pointed, setiferous projections. Metasome very narrow, with the epimera of the 5 anterior segments produced to spiniform projections densely clothed with long ciliated bristles, terminal segment narrow and elongated, equalling in length the other 5 combined, subcylindrical in form and furnished laterally with numerous small setiferous nodules. Eyes imperfectly developed, with opaque whitish pigment and devoid of any distinct visual elements. Superior antennae rather elongated, 1st joint of the peduncle attenuated distally and finely serrated in the proximal half of the inner edge, flagellum fully as long as the peduncle and 16 20-articulate, accessory appendage about half as long, and 8 9-articulate. Inferior antennae with the flagellum longer than the peduncle. Chelipeds in female rather robust, scarcely smaller than the fossorial legs, basal joint fusiform, with a strong denti- form projection on the posterior edge beyond the middle, hand much larger than the carpus, oblong ovate in form, thumb with a distinct tubercle in the middle of the inner edge; those in male with the hand very large and tumid, both the thumb and the dactylus strongly tubercular inside. Uropoda very much elongated, attaining almost half the length of the body, inner ramus composed of about 30 articulations, outer ramus scarcely Ys as long and 1 2-articulate. Colour whitish. Length reaching to 13 mm. Remarks. - - The present species was briefly described by my late father in the year 1858 as Rhwa spinosa, but was subsequently, by most authors, identi- 8 fied with Apseudes talpa of Montagu. Having, however, been enabled to examine the latter species from Mediterranean specimens, I have convinced myself of its distinctness from the Norwegian form. The latter grows to a much larger size than the typical species, and has the body more strongly spinous. differing more- over very conspicuously in the rudimentary condition of the eyes, which in A. talpa, on the other hand is well developed, with dark pigment and distinctly defined visual elements. Occurrence. - - The species occurs along the whole coast of Norway, from the Christiania Fjord to Yadso on a bottom consisting of loose muddy clay with gravel or stones intermingled, the depth ranging from 30 to 150 fathoms. It is a rather sluggish animal, concealing itself in the loose mud, so that at first it is not easily caught sight of. In many cases, moreover, it is found to be so thickly covered with mud adhering to the several spiniform projections of the body, and to the setae issuing from them, that it is rather difficult to recognise. I have never seen it make any attempt to swim, though the structure of the pleopoda would seem to allow it. at least in a younger state, to move at times freely through the water. Distribution. - - Bohuslan (Lilljeborg); SSW of Ireland (Porcupine Expe- dition) in a depth of 725 fathoms (Norman & Stebbing). Gen. 2. SphyrapUS, Norm. & Stebb., 1884. Generic characters. - - Body less elongated than in Apseudes, though some- what more slender in male than in female. Cephalosome broadest behind and gradually narrowed in front, upper face vaulted and less distinctly areolated, frontal plate imperfectly defined at the base. Ocular lobes very small. First free segment of mesosorne rather broad, and firmly connected with the cephalosome, but not coalesced with the same, coxal plates very small, not produced in the form of spines. Metasome not very much elongated, terminal segment comparatively short. Eyes wholly absent. Superior antennae with the 1st joint of the peduncle rather large and flattened, accessory appendage small; flagelluni in male with dense bunches of sensory filaments. Inferior antennae very slender and without any scale-like appendage. Mandibles comparatively less strong than in Apseudes, palp very slender and only thinly setous. Chelipeds with the hand very large, sub- malleolate, being set on at right angles to the carpus, the latter, as also the rneral joint, much more elongated in male than in female. Fossorial legs in male of extraordinary length. Pleopoda well-developed, with both ranii biarticulate. Uropoda of moderate length, and of a similar structure to that in Apseudes. Remarks. - - This genus has been established by Messrs. Norman & Stebbing, to include some forms differing from Apseudes, among other things, in the absence of the scale-like appendage to the inferior antennae. As another distinctive character, is mentioned the supposed fusion of the first 2 segments of the meso- some with the cephalon ; but this, I believe, is not quite correct. For in the Nor- wegian species, at any rate, the 2nd segment is well defined from the cephalosome, though apparently rather firmly connected with it. As a third characteristic feature may be mentioned the ven pronounced sexual difference occurring in this genus, both as to the general form of the body, and to the structure of the superior antenna? and the first 2 pairs of legs. The generic name refers to the peculiar malleolate appearance of the chelipeds, which, especially in the male, is very conspicuous. We know as yet of 4 species, 2 of which, S. malleolus and S. hides, were procured during the Porcupine Expedition from very considerable depths, the greatest being 1460 fathoms, the 3rd, S. serratus Gr. 0. Sars, likewise from great depths in the Arctic Ocean, the 4th a Norwegian form, to be described below. Sphyrapus anomalus, G. 0. Sars. (PI. Ill & IV.) Apseudes anomaltts, G-. 0. Sars, Undersogelser over Christianiafjordens Dj'bvandsfauna, N. Mag. f. Naturvid. f. 1869, p. 45. Specific Characters. Body in female scarcely 5 times as long as it is broad, in male considerably more slender. Cephalosome with the upper face evenly vaulted and perfectly smooth, frontal plate broad, rounded, exserted at the end to a short, finely denticulated point. First free segment of mesosome somewhat broader than the cephalosome; the succeeding ones much narrower and defined by deep constrictions; last segment shorter than the others. Metasome perfectly smooth, with the epimera not at all produced, terminal segment occupying about y 3 of the length of the metasome and obtusely rounded at the tip. Superior antennae in female about the length of the cephalosome, 1st joint of the peduncle gradually widening distally, with 4 strong setse on the outer edge, last joint very small; flagellum scarcely half the length of the peduncle, and 5-articulate, acces- sory appendage about half its length, and 3-articulate; those in male rather larger, flagellum more fully developed, 7-articulate, and carrying dense fascicles of sensory filaments. Inferior antenna? fully as long as the superior, but much narrower, flagellum much shorter than the peduncle, and 4-articulate. Chelipeds v & v 2 Crustacea. 10 in female rather strong, hand very large oblong oval, malleolate, exceeding in length the 2 preceding joints combined, fingers about the length of the palm and densely serrated inside. Chelipeds of male much more elongated, with the basal joint exceedingly large, and the meral joint greatly elongated and narrow. Fos- sorial legs in female longer than the chelipeds, and in male almost attaining the length of the whole body, the carpus being greatly elongated. Ambulatory legs narrow, and but scantily setiferous. Uropoda scarcely exceeding in length the metasome, inner ramus 10-articulate, outer rather small and 3-articulate. Colour a pure white. Length of female 4 mm., of male 5 mm. Eemarks. - - The present form was first recorded by the author under the name of Apseudes anomalus. It certainly belongs, however, to the genus Spliyrapus subsequently established by Messrs. Norman and Stebbing. It is very nearly allied to the arctic species, 8. serratus, described by the present author from the Norwegian North Atlantic Expedition, but may be at once distinguished by the fact that the epimera of the metasome are not, as in that species, acutely produced, but are simple and rounded. Occurrence. I have met with this form along the whole Norwegian coast from the Christiania Fjord to Vadso. In the great fjords especially, it is often found in rather large numbers on a bottom consisting of muddy clay, the depth ranging from 100 to 400 fathoms. It is accordingly, like the other species of the genus, a true deep-water form, and resembles in habits the species of the genus Apseudes. Distribution. The Kara Sea (Hansen). Fam. 2. Tanaidae. Body sublinear, cylindric, scarcely attenuated behind. Cephalosome not very broad, scarcely depressed, and having the front, as a rule, narrowly trun- cated; ocular lobes sometimes well defined, sometimes obsolete. Free segments of mesosome perfectly smooth, the middle ones being generally the longer; coxal plates inconspicuous. Metasome comparatively short, but scarcely narrower than the mesosonie. Eyes present or wanting. Superior antenna? issuing close together from the frontal part, simple, in female comparatively short, conical and composed of only 3 or 4 articulations, in male, as a rule, much more fully developed, with a well-defined, multiarticulate flagellum. Inferior antennas generally smaller 11 than the superior, flagellum short, and, as a rule, only Inarticulate. Mandibles of various structure in the several genera, but always without palps. Anterior maxilla? with only a single slender masticatory lobe; posterior ones quite rudimentary, forming simple rounded lobes. Maxillipeds coalesced at the base, epignath generally narrow, falciform. Chelipeds, as a rule, strongly built and closely applied to the oral area, issuing from the posterior part of the cephalo- sonie with a broad base, carpus generally broad and compressed, hand some- times rather dissimilar in the two sexes. Second pair of legs not very different from the succeeding ones, being rather small and ambulatory in character. Pleo- poda, as a rule, very small, with the rami lamelliform and incurved, sometimes in female rudimentary or quite wanting. Uropoda not much elongated, simple or biramous. Remarks. - - This family may be easily distinguished from the preceding one, both as regards the outward appearance of the body, and the structure of the several appendages. It comprises rather a large number of genera, amounting to about 1 5 in all. These genera are chieliy characterised by the structure of the mandibles, partly also by that of the superior antenna?, the legs and the several appendages of the metasome. As to habits, the greater part of the species perhaps all seem to be tubicolar in character, constructing for themselves abodes of mud, into which they may wholly withdraw their bodies. They all, moreover, exhibit this peculiarity, namely, that on reaching the surface of the water, they remain floating, without being able to reimmerge their bodies, whereby the dis- covery of the generally very small and inconspicuous specimens is essentially facilitated. On placing some muddy clay taken from greater depths, in a shal- low vessel, and stirring up the mud, they will very soon appear floating on the surface like small white pins, and may easily be taken up for a closer examina- tion. To the Norwegian fauna belong 11 different genera, to be described below. Gen. 1. TanalS, M.-Edw., 1829. Syn. Crossurus Eatlike. Generic Characters. - - Body not much elongated, but with the cephalosome rather tumid and provided with distinctly defined ocular lobes. Metasome only composed of 5 segments. Eyes well developed. Superior antenna? of similar structure in the two sexes, 3-articulate, with a very small knob-like terminal 12 flagellum. Inferior antennae a little smaller than the superior, with the flagellum 3 4-articulate. Mandibles rather strong, with the molar expansion well-developed. Palp of the anterior maxillae biarticulate and provided at the tip with several slender setae. Epignath of the maxillipeds more fully developed than in most other Tanaidae, forming a semilunar, ciliated plate terminating in a digitiform lappet. Chelipeds very robust, especially in the male, hand in the latter much larger than in female, and having the fingers subforcipate. Second pair of legs slightly differing from the succeeding ones, the dactylus being very much elongated and setiform; dactyli of the other pairs strongly hooked, and in the 3 posterior pairs armed with comb-like teeth. Only 3 pairs of pleopoda present, all of them rather fully developed, with densely setiferous lamelliform rami. Uropoda simple, not much elongated, and composed of a limited number of articulations. Incubatory pouch formed by 2 lamellae only, issuing from the base of the 5th pair of legs. Remarks. - - This is the first recorded genus, and from it, therefore, the whole family has been named. It is well distinguished from all the other genera, especially by the structure of the metasonie and the limited number of pleo- poda. The genus contains as yet 4 species, viz., T. tomentosus Kroyer, T. Caro- lini M.-Edw., T. Dulonyi M.-Edw. and T. novw-zcalandice Thomson. Only the first-named of these species occurs off the coasts of Norway. Tanais tomentosus, Kroyer. (PI. v.) Tanais tomentosus, Kroyer, Naturli. Tidsskr. Bel. IV, p. 183. Syn : Orossurus rittatns, Bathke. Tanais vittatus, Lilljeborg. Tanais liirticaudatus, Sp. Bate. Specific Characters. - - Body of female about 5 times as long as it is broad, that of male somewhat shorter and thicker. Cephalosorne rather tumid in its posterior part, and gradually narrowed anteriorly, frontal edge slightly angular in the middle. Free segments of niesosonie defined by well-marked and rather deep constrictions, the 3 posterior ones being somewhat longer than the 3 anterior, and widening behind. Metasonie fully as broad as the niesosonie, but considerably narrowed in its posterior part, the 3 anterior segments being much the largest, and densely clothed laterally with stiff bristles, which on the 2 foremost ones are continued across the dorsal face in band-like fringes; 4th segment very small, terminal one scarcely broader, and subquadrangular in form. Eyes well developed, with dark pigment and distinct visual elements. Superior antennae in female 13 shorter than the cephalosome, and rather densely setiferous at the end of the joints, 1st joint about the length of the remaining joints combined, olfactory filaments 5 in number. Inferior antennae but little shorter than the superior, though somewhat narrower. Chelipeds very strong, hand in female oblong oval and exceeding in length the carpus, both fingers provided inside with an obtuse tubercle; that in male considerably larger, with the fingers distinctly forcipate. 1st pair of pereiopoda longer than the others, dactylus Inarticulate and subulate in shape ; the succeeding ones with the carpal joint somew r hat expanded and armed with several strong denticles, dactylus in the 3 posterior pairs very strong, hooked and armed inside in their outer part with comb-like denticles. Uropoda about the length of the last 2 segments of metasome combined, 3-articulate and rather densely setiferous, middle joint the longest, terminal joint rather short. Body whitish, variegated on the dorsal surface with a dark brownish pigment form- ing on the cephalosome a close reticulation, on the segments of mesosome, inter- rupted transversal bands. Length of adult female 5 mm., of male somewhat less. Remarks. - - This form has been recorded by Kroyer, as early as in 1842, under the above name, whereas Rathke's description of his Crossurus vittatus dates from the succeeding year. According to the rules of priority therefore, the specific name proposed by Kroyer ought to be preferred to that of Rathke. The T. Cavolini of M.-Edw. is very closely allied to the present species, and the only, in any way essential difference I have found in examining a single specimen of that species, is that the uropoda are 4-articulate instead of 3-articulate. Occurrence. - - Rathke found this form on oysters at Molde. It has sub- sequently been observed at Christiansund by v. Diiben, and on the south coast by Orsted. My late father found it at Floro and Manger. I have myself ob- served it rather plentifully in a small bay at Korshavn, south of Bergen, where it occurred in quite shallow water among grass. At Haugesund, farther south, I have found it occasionally in weedy pools left by the tide. Distribution. -- Oresund (Kroyer). British Isles (Sp. Bate), Atlantic coast of North America (Harger). Gen. 2. Heterotanais, a. o. Sars, isso. Generic Characters. Body comparatively short and thick, slightly depressed, and exhibiting a rather different appearance in the two sexes. Metasome nor- mally developed, with all 6 segments well defined. Eyes distinct, placed, as in 14 Tanais, on separate lobes. Superior antenna? in female short, inarticulate, with only a single terminal olfactory filament, in male more elongated, with the flagel- luni more or less developed. Mandibles rather strong, cutting edge in the left one consisting of 2 superposed dentated lamella?, in the right mandible simple and finely serrated on the front edge, molar expansion in both mandibles large and thick. Palp of anterior maxilla? uniarticulate, terminating with 2 seta? only. Epignath of maxillipeds narrow falciform. Oral parts in male quite abortive. Chelipeds in female normal, in male very different, being imperfectly chelate, thumb very short, or transformed to a posteriorly-pointing lappet. 1st pair of pereiopoda longer than the others, with the dactylus setiform; the succeeding ones comparatively short and stout, with the dactylus simple. Pleopoda normal. Uropoda biramose, outer ranms very small, inner elongate, 4 5 articulate. In- cubatory pouch normal. Remarks. - - This genus was established by the present author in 1880, to inilude Tanais Orstedi of Kroyer, which in some points differs rather markedly from the other Tanaidse. though being most nearly allied to the genus Leptoclieria of Dana. From the latter it differs chiefly in the very anomalous structure of the chelipeds in the male. Besides the typical form, another species has been described by the present author from the Mediterranean as H. anomalus. Moreover, the north American form Leptochelia limicola Harger, and the New Zealand species Paratanais tenuis Thomson, are most probably referable to this genus. Heterotanais Orstedi, Kroyer. (PI. VI.) Tanais Orstedi, Kruyer. Nat. Tidsskr. Bd. 4. p. 183. Syn: Tanais curculio Kvoyer cf. ,. laWiicits Fr. Miiller 9- rhi/nchites Fr. Miiller cf. Specific Characters. Body about 5 times as long as it is broad, with the cephalosome in female of normal appearance, equalling in length the 3 succeeding segments combined, in male strongly produced and abruptly narrowed in front to a cylindrical neck, carrying on the tip the antenna? and eyes. Segments of mesosome much more densely crowded in male than in female. Metasome in male about half the length of the mesosome, in female scarcely longer than the last 2 segments combined, terminal segment comparatively short and obtusely rounded at the tip. Eyes of moderate size and same appearance in the two sexes. Superior antenna? in female shorter than the cephalosome, with the basal 15 joint nearly twice as long as the other 2 combined, in male considerably more elongated, and composed of 5 articulations successively diminishing in size, the outer 2 representing the flagellum. Chelipeds in female of moderate size, hand oval, with the ringers comparatively short, the thumb having, inside, 3 serra- tions, the dactylus a single tubercle; those in male of enormous size, carpus very large and produced in front, outside the hand, to a lamellar lobe, hand imper- fectly chelate, the thumb being transformed into a thin, reflexed lappet instricted at the base, dactylus long and falciform, with 3 small denticles inside. First pair of pereiopoda much larger than the others, the 3 posterior pairs more strongly built than the 2 preceding ones, with the basal joint rather tumid. Uro- poda about half the length of the nietasome, inner ramus 4-articulate, outer very small and biarticulate. Colour whitish. Length of adult female 2 mm., of male about the same. Remarks. The very pronounced sexual difference occurring in the present form has caused it to be twice described under 2 different names. Kroyer de- scribed the female as Tanais Orstedi and the male as T. curculio, and some years afterwards Fr. Mliller, having apparently not been aware of Kroyer's description, recorded the same form under 2 different names, viz. : Tanais balthicus (the female) and T. rhynchites (the male). In this manner therefore, no less than 4 different names have been assigned to the same species. As Kroyer was the first to observe the species, one of his 2 specific names ought to be retained for the species, and more properly that by which the female was described. From the Mediterranean species, H. anomalus, the present form is easily distinguished by the very different aspect of the male. Occurrence. I have taken this form rather plentifully in the Iddefjord at Fredrikshald, wh^re it occurred on a muddy bottom at a depth of 3 6 fathoms. Male specimens were, as usual, far less frequent than female ones, of which numerous specimens, both young and adult, were collected. Some specimens of this form are moreover contained in our University Museum, having been taken by the late Dr. Boeck from piles of the quay at Christiansand. Distribution. Oresund (Kroyer), Baltic at Landskrona and Westervik (Lilljeb.), Prussia at Greifswalde (Fr. Milller), Bohuslan (Lilljeb.). 16 Gen. 2. Paratanais, Dana, 1852. Generic Characters. Body of female linear, more or less elongated, of male much shorter and stouter. Cephalosome and metasonie in both sexes normal. Eyes distinct, being much larger in male than in female, superior antenna 3 in female conical, 3-articulate, in male much more fully developed, consisting of a biarticulate peduncle and a well-defined 4-articulate flagellum densely clothed with sensory filaments. Mandibles well-developed and of a structure similar to that in the preceding genus. Oral parts in male, with the exception of the niaxillipeds, abortive, epistome greatly produced. Chelipeds in both sexes nor- mal and not very dissimilar, hand oblong oval, fingers comparatively short. Pereiopoda of moderate size, 1st pair slightly differing from the others, and having the dactylus setiform, the 3 posterior pairs much stronger than the 2 prece- ding pairs, though having the basal joint not much tumefied. Pleopoda all well developed, being comparatively larger in male than in female. Uropoda small, biramose, rami subequal and biarticulate. Incubatory pouch normal. Remarks. This genus was established in the year 1852 by Dana, to in- clude a small Tanaid from the Sooloo Sea, P. elongatus. Several species have been subsequently adduced to this genus, but the greater part of them are in my opinion evidently generically distinct, and at the present time only a single additional species is to be noted, viz., the one described below. The genus is somewhat intermediate in character between the genera Leptochelia and Typhlo- tanai.Sj though differing in some points rather markedly from both of them. Paratanais Batei, G. 0. Sars. (PI. VII.) Paratanais Batei, G. 0. Sars, Revision af Gruppan Isopocla chelifera, p. 32. Syn : Paratanais fortipatus, Sp. Bate (not Lilljeb.) Specific Characters. Body of female about 5 times as long as it is broad, slightly tapering in front and behind, that of male much shorter and conspicuously constricted in the middle. Cephalosome in female gradually tapering anteriorly, with the frontal margin slightly angular in the middle; that of male not having the anterior part prolonged; ocular lobes in both sexes imperfectly defined. Metasonie in female scarcely as broad as the mesosome and furnished laterally with scattered hairs, terminal segment about the length of the 2 preceding ones combined, and evenly rounded at the tip. Eyes in female comparatively small, though distinct, in male very large, oval, with numerous refracting cornese. Superior antenme in female shorter than the Cephalosome, basal joint somewhat 17 exceeding in length the other 2 combined, terminal joint longer than the penul- timate one; those in male attaining almost y 3 of the length of the body, 1st joint of the flagellum very short, discoidal and, like the 2 succeeding joints, having a dense bunch of olfactory filaments. Chelipeds in female somewhat tapering distally, hand a little longer than the carpus, and oblong oval in form, with the fingers much shorter than the palm; those in male slightly differing, the hand being conspicuously dilated in the middle. Uropoda about the length of the lust 2 segments of metasome combined, outer ramus a little shorter and narrower than the inner, joints of the rami of equal length. Length of adult female 1.60 mm., of male 0.90 mm. Remarks. This form was first recorded by Sp. Bate, but was errone- ously identified by him with Tanais forcipatus Lilljeborg, which belongs to a very different genus. It was therefore necessary to change the specific name, and in 1880 I proposed for the species the, name of P. Bedel. From the type species, P. elongatus Dana, it is easily distinguished by its much less slender form, the male especially exhibiting quite an unusually short and thick body. Occurrence. I have met with this form in several places on the west coast of Norway, in comparatively shallow water among the roots of Laminarise. The males, as usual, are far less numerous than the females and, on the whole, look so very different, that they may easily be mistaken for quite a different species. As however, they, were found in company with the females, and no other Tanaid occurred in these places, their true relation could with certainty be affirmed. Distribution. "British Isles (Sp. Bate), Mediterranean at Spezia (the author). Gen. 3. TyphlOtanaiS, G. O. Sars, 1880 Generic Characters. - - Body in female more or less elongated, sub-depressed, linear, with the lateral contours almost straight; that of male comparatively shorter and constricted in the middle. Cephalosome of moderate size, narrowly truncated in front, or slightly produced in the middle, with no traces of ocular lobes. 1st free segment of mesosome generally much shorter than the others. Me- tasome normal. Eyes wholly absent. Superior antenme in female conically attenuated, 3-articulate, with the middle joint small, the terminal one narrow and elongated; those in male much larger and of a similar structure to that in *& i 3 Crustacea. 18 the genus Parataitais. Inferior antennae, as a rule, rather narrow, with the 2nd joint more or less dilated. Mandibles well-developed, cutting edge obscurdv dentated and provided on the left mandible with a distinct secondary lamella, molar expansion cylindric, straight, and slightly dilated at the tip, which is transversely truncated, and surrounded with dentiform tubercles. Oral parts in male, excepting the maxillipeds, abortive; epistome prominent, globular. Chelipeds in female less robust, generally attenuated distally, with the hand comparatively narrow, and the fingers simple; those in male but slightly different. 1st pair of pereiopoda, as a rule, longer than the second, with the dactylus setiform; the succeeding ones comparatively short, basal joint of the .'} posterior pairs generally strongly tumefied. Pleopoda normally developed and larger in male than in female. Uropoda short, hiramose, both rami Inarticulate, or one of them uniarticulate. Incubatory pouch normal. Remark*. This genus is chiefly distinguished from the preceding ones by the total absence of eyes ;md ocular lobes, as also by the somewhat dim-rent structure of the mandibles. Moreover the subulate form of the superior antenna 1 in the female, and the narrowness of the hand of the chelipeds may serve as recognizing marks. The genus contains rather a large number of species, which all are true deep-water forms, and pronouncedly tubicolar, constructing small cylindric tubes of mud-particles agglutinated together. No less than 9 different species occur off the coast of Norway, and will be described below. Moreover the present author has recorded a Mediterranean species. T. 'iii<'xxhi<')ixi*. and 2 additional species, T. krri/at'ln/x/s and T. I>rnrlt//nrti* have been described by Mr. F. Beddard from the Challenger Expedition. 1. Typhlotanais tenuimanus (Lilljeb.). (PI. VIII, fig I.) Tint/us tenuimanus, Lilljeboi-o-, Bidrn.u- till Ki'mnedomen om ilo inoni Svi-ri^p och Norrige fore- konnnande Crustaceerne af Tanaidernes fnniilj, p. 15. Specific Character*. Q. Body more than (i times as long as it is broad, with the segments only separated by very narrow constrictions. Cephalosome rather large, much longer than it is broad, and gradually attenuated in front. 1st free segment of mesosome much shorter than the others, the 4 succeeding ones subequal, rectangular, last one somewhat shorter. Metasome slightly dilated in the middle, with the terminal segment about the length of the 2 preceding ones combined. Superior antenna 1 but little shorter than the eeplmlosome, subulate, terminal joint much elongated ;md narrow, nlmost attaining the length of the basal one. Inferior antenna with the 2nd joint of the peduncle considerably dilated. Chelipeds much attenuated, hand very narrow, and not nearly attaining the length of the carpus, fingers shorter than the palm. 1st pair of pereiopoda longer than the others; the 2 succeeding pairs comparatively robust, with Hu- meral joint dilated distally, triangular in form, and carrying inside a strong spine; the 3 posterior pairs likewise strongly built, with the basal joint much tumefied. ;iiid the 2 outer joints minutely serrulate on the inner edge. Uropoda attaining half the length of the metasome, both rami biarticulate and rather narrow, especially the outer one, which scarcely exceeds in length the basal joint of the inner, and has its terminal joint about twice the length of the basal one. Length reaching to 4.20 mm. Remarks. - - This is the largest and finest species of the genus, and may, moreover, easily be recognized by the strongly attenuated chelipeds and the structure of the uropoda. It may be regarded as the type of the genus, Occurrence. I have met with this beautiful form in numerous places on the Norwegian coast, from the Christiania Fjord up to the Lofoten Isles, in depths ranging from 50 to 300 fathoms. In some places, for instance in the Cliristiania Fjord south of Drdbak. it occurs in considerable numbers on a bottom of loose muddy ('lay, covered with decaying /ostera. The specimens examined by Prof. Lilljeborg were procured at Molde. Out of Norway, it has not yet been recorded. 2. Typhlotanais mieroeheles, (I. 0. Sars. (PI. VIII, fig. 2.) lyphlotanais mieroeheles, Or. O. Sara, I. c. \\. .'ody somewhat more slender than in the pre- ceding species, being about 7 times as long as it is broad, and having the seg- ments more sharply marked oil' from each other. Cephalosonie gradually attenu- ated anteriorly, frontal margin acutely produced in the middle. First free segment of mesosome rather short and somewhat widening in front; the remaining seg- ments subquadrate in outline. Metasome scarcely broader than the mesosome, and having the terminal segment rather short. Superior antenna? comparatively short, but little exceeding halt' the length of the cephalosome, conical in form, basal joint longer than the other 2 combined, terminal joint produced at the tip to a somewhat inward-pointing denticle. Inferior antenna 1 with the 2nd joint of the peduncle less dilated than in the preceding species. Chelipeds rather poorly developed, hand unusually small and narrow, with the fingers about the length of the palm. 1st pair of pereiopoda not very different from the 2 succeeding pairs, though with the dactylus more produced. The 3 posterior pairs less 20 robust than in T. tenuimanus, with the basal joint less tumid, and the 3 outer joints each armed inside with a strong denticle. Uropoda about half the length of the metasome, rami very narrow and unequal, the inner Inarticulate, the outer uni- articulate and scarcely more than half as long. Length 2.70 mm. Remarks. - This species is nearly allied to T. tenuimanus, though easily distinguishable by several well-marked differences, for instance, the acutely pro- duced frontal margin, the comparatively short superior antennae, the unusually poor development of the chelipeds, and the structure of the uropoda. Occurrence. Only a few female specimens of this form have hitherto been found by me. These were collected in two widely-distant localities, viz., at Bekkervig, on the west coast of Norway, and at Kvalo on the Nordland coast, the depths being 60 100 fathoms. 3. Typhlotanais fmmarehieus, G. 0. Sars. (PI. IX.) Typltlotanais finmarchicus, G. O. Sars, 1. e. p. 36. Specific Characters. - - Body in female sublinear, depressed, about 6 times as long as it is broad, with the segments only separated by narrow constrictions; that of male less elongated, with the segments more sharply marked off from each other. Cephalosome in female almost as broad as it is long, with the side-contours evenly arcuate; that in male considerably more narrowed in front. 1st free segment of mesosome in female about same size as the last one, the 4 middle ones considerably larger and rectangular. Metasome in female of nearly equal breadth throughout, in male much more fully developed, subfusiform and occupy- ing Vs f the length of the body. Superior antenna? in female scarcely attaining the length of the cephalosome, basal joint almost twice as long as the other 2 combined; those in male modified in the usual manner, basal joint very large and laminar, slightly widening distally. Chelipeds in female of moderate size, hand slightly dilated in the middle and nearly as long as the carpus, fingers about the length of the palm; those in male somewhat more feeble, with the hand narrower and provided inside the insertion of the dactylus with a transverse row of about 5 se.tse. 1st pair of pereiopoda a little longer than the succeeding pairs, and having the dactylus more produced; the 3 posterior pairs moderately strong, with the b;isal joint not much tumefied, and the carpal joint forming a smooth, rounded prominence at the end inside. Pereiopoda in male comparatively more slender than in female. Uropoda rather short, scarcely exceeding l / s of the length of the metasome, both rami distinctly Inarticulate, the outer one shorter and much narrower than the inner, both articulations equal in size. Body in female whitish, semipellucid, each of the segments of the uiesosome having 1 irregular, juxtaposed patches of a light yellowish colour derived from some opaque matter lying inside the skin; that of male slightly variegated with a pale brownish pig- ment. Length of female 2.00 mm., of male 1.50 rum. Remarks. This form, at first sight, looks rather like T. cequiremis Lilljeborg, to be described below, but is found, on a closer examination, to differ in the structure of the superior antennae, the posterior pairs of pereiopoda, and the uropoda. It is also rather inferior in size. Occurrence. I found this species, many years ago, rather plentifully in the harbour of Vadso at a depth of 30 fathoms. Male specimens occurred not infrequently together with the females, and could of course with perfect certainty be referred to this species. Otherwise it is a matter of great difficulty to refer male specimens to their respective species, not only because they differ very markedly from the females, but because they exhibit a perplexing mutual similarity. 4. Typhlotanais aeqviremis (Lilljeborg). (PL X, fig. 1). Tanais ceqviremis, Lilljeborg, 1. c. p. 21. Syn: Tanais depressus, G. O. Sars (oliin). Specific Characters. - - 9- Body linear, more than 6 times as long as it is broad, and pronouncedly depressed, with the cephalosome rather short, but little longer than it is broad. First free segment of mesosonie shorter than the others, which are rectangular in form. Metasome scarcely longer than the hist 2 seg- ments of mesosonie combined, and of equal breadth throughout, terminal seg- ment comparatively short, and obtusely truncated at the tip. Superior antennse about the length of the cephalosome, conically tapering, basal joint somewhat longer than the other 2 combined. Chelipeds comparatively strong, hand larger than usual, attaining the length of the carpus, and oblong oval in form, fingers about the length of the palm. 1st pair of pereiopoda considerably longer than the 2 succeeding ones, which are rather small; the 3 posterior pairs very robust. with the basal joint exceedingly tumefied, and the carpal joint quite smooth, not- produced inside. Uropoda very short, but little longer than the terminal segment of the metasome, rami subequal in length, the outer one distinctly bi articulate and terminating in a rather strong seta, inner ramus uniarticulate, though so-netimes with a very slight indication of a subdivision beyond the middle. Length 3.10 mm. 22 Remark*. - This form was first recorded by the present author as a new spe- cies under the name of Tanais depressus. I have, however, subsequently convinced myself that in reality it is identical with the form described by Prof. Lillj-borg at an earlier date, as Tanais ceqviremis. The species may be recognized by the pronouncedly depressed form of the body, the comparatively strong chelipeds and the structure of the uropoda. Prof. Lilijeborg states that both rami of the latter are biarticulate, but the inner one does not in fact exhibit any distinct subdivi- sion. and may mor properly be said to be uniarticulate. Occurrence. The species is rather common along th-i- whole south and west coasts of Norway, in depths ranging from 30 to 100 fathoms. It extends north- wards to the Lofoten Isles. Distribution. Bohuslan (Lilljeb.) 5. Typhlotanais assimilis, G. 0. Sars. (PI. X, fig. 2). Typhlotanais assimilis, G. 0. Sars, 1. c. p. 3(i. tiT*. 9- Body rather slender, linear, subdepressed, about 7 times as long as it is broad, with the cephalosome comparatively large, excee- ding in length the 2 anterior segments of the mesosonie combined, and but slightly narrowed in front. 1st free segment of mesosonie considerably shorter than the others, which arc rectangular in shape. Metasome longer than the last 2 segments of mesosoine combined, terminal segment about the length of the 2 preceding ones taken together, and obtusely produced at the tip. Superior an- tenme rather elongated, conically tapering, with the basal joint but little longer than the other 2 combined, terminal joint long and narrow. Inferior antenna^ with the 2nd joint of the peduncle rather expanded and finely serrated on the upper edge. Chelipeds not nearly so strong as in T. ii'ijriri'ini*. and attenuated distally, hand about the length of the carpus, but much narrower, fingers shorter than the palm. 1st pair of pereiopoda much longer than the 2 succeeding ones, which are very small, with the propodal joint oblong oval in form and somewhat compressed; the 3 posterior paivs resembling in structure ^hose in T. o't/rirciii/*, though having the basal joint less tumefied. Uropoda somewhat longer than the last segment of the met.-isome, both rami distinctly biarticulate and rather unequal, the outer one being much shorter than the, inner, though scarcely narrower. Length 1.70 mm. It'i'iiittrf,-*. The present species is nearly allied to T. fi'lil different localities of the Norwegian coast, lying rather widely distant from each other, viz., in Kidsfjord west of Listerland, at Bekkervig south of Bergen, and at Kvalo on the Nordland coast, the depth ranging from (ill to 120 fathoms. 7. Typhlotanais brevicornis (Lilljeb.) (I'l. XL, tig. 1). lin-rii'iinii*. Lilljfhnrn', I.e. p. 1">. HiH'cifi-c ('liiirftctcrs. - ( . Body extremely slender and narrow, about ! time> as long as it is broad, with the cephalosome gradually tapering in front. 1st 24 free segment of mesosonie longer than the last one, and not much shorter than those immediately succeeding it. Metasome about the length of the last 2 segments of niesosome combined, terminal segment evenly rounded at the tip. Superior an- tenna? rather short, scarcely more than half as long as the cephalosome, basal joint much longer than the other 2 combined. Chelipeds of moderate size, hand oblong in form and somewhat shorter than the carpus, lingers about the length of the palm. 1st pair of pereiopoda considerably longer than the others, the 3 posterior pairs rather short, with the basal joint not much tumefied. Uropoda scarcely longer than the terminal segment of metasome, rami very unequal, the outer one extremely small and uniarticulate, pointing generally straight outwards, inner ranius more than twice as long, and distinctly biarticulate. Length 1.60 mm. Remarks. The present species, established by Prof. Lilljeborg, is easily recognized by the very slender and narrow body, the comparatively short superior antennae, and the structure of the uropoda. Occurrence. I have met with this species not infrequently in several places both on the south and west coasts of Norway, in depths ranging from 60 to 150 fathoms. It extends northwards to Kvalo on the Nordland coast. Distribution. Coast of Denmark (Meinert). 8. Typhlotanais cornutus, G. 0. Sars. (PL XI, fig. 2). Paratanais cornutus, G. 0. Sars, Crustacea & Pycnogonida nova in itinere 2do et 3tio Expedi- tionis Norvegicte anno 1877 & 78 collecta, No. 5. Specific Characters. $. Body comparatively short and thick, depressed, about 4 ] /2 times as long as it is broad, with the cephalosome rather broad in proportion to its length, and evenly convex on each side, frontal margin pro- duced in the middle to an acute rostriform projection. 1st free segment of niesosome very short, the others more than twice as broad as they are long, and separated by narrow constrictions. Metasome considerably longer than the last 2 segments of mesosome combined, and slightly narrowed in its distal part. Superior antennae about the length of the cephalosome, conically tapering, basal joint somewhat longer than the other 2 combined, terminal joint rather narrow and tipped by slender bristles. Chelipeds of moderate size, and somewhat attenuated distally, hand scarcely attaining the length of the carpus, and oblong oval in form, fingers shorter than the palm. 1st pair of pereiopoda, as usual, longer 25 than the 2 succeeding pairs, basal joint of the 3 posterior pairs rather tumid. Uropoda equalling in length about y 3 of the meta.sniiie, both rami distinctly bi- articulate and somewhat unequal, the outer one being shorter and narrower than the inner. Length 1.65 mm. Remarks. - - This form was discovered during the Norwegian North Atlantic Expedition, and has been described and figured in detail by the present author in the Report of the Crustacea from that Expedition. It is easily distinguished from any of the previously described species by its comparatively short and thick body, the acutely produced frontal margin, and the comparatively long bristles issuing from the tip at' the superior antennae. Occurrence. - - A few female specimens of this form have been taken by me at Kvalo on the Nordland coast, from depths of 60 100 fathoms. Distribution. Stat. 290 of the Norwegian North Atlantic Expedition, lying W. of Finmark. 9. Typhlotanais penieillatus, G. o. Sars. (PI. XI, fig. 3.) Typhlotanais penicillatus, (I. O. Sars, 1. c. p. 39. Specific Characters. - 9- Body a little more slender than in T. cornutus, being almost 5 times as long as it is broad. (Jephalosome not nearly so broad as in the said species, and having the frontal edge less strongly produced in the middle. First and last segment of mesosome of about same size and somewhat shorter than the others, which are separated by rather conspicuous constrictions. Metasome of almost uniform breadth throughout. Superior antennae extremely slender and narrow, considerably exceeding in length the cephalosome, terminal joint linear and tipped by slender bristles, one of which is of quite an unusual length. Chelipeds slender and feeble, hand very narrow, sublinear, exceeding in length the carpus, fingers nearly as long as the palm. Pereiopoda resembling in structure those in T. cornutus, basal joint of the 3 posterior pairs, however, less tumid. Uropoda with the inner ramus distinctly Inarticulate, the outer one uni- articulate and somewhat shorter. Length 1.40 mm. Remarks. - - This species is nearly allied to T. cornutus, but is of somewhat more slender form, and moreover easily distinguished by the much feebler struc- ture of the chelipeds, and by the extremely slender superior antennae, with their long terminal pencils of bristles. Also the uropoda differ essentially in the fact of the outer ramus being uniarticulate. 4 Crustacea. 26 Occurrence. Only 2 female specimens of this form have hithertho been t.-ikcii by me. They were collected at Sauesund, west coast of Norway, from depths of 50 to 10U fathoms. Gun. 4. Leptognathia, a. o. Sars, isso. Generic Characters. Body in female, as a rule, narrow and elongated, snbcylindrical, with the segments marked off by marked constrict inns ; that of male much shorter and stouter. ( Vphalosome generally narrowed only in its most anterior part, and having the front narrowly truncated. Metasome with all its segments well defined, being much more fully developed in male than in female. Eyes wholly absent. Superior antenna.' in female distinctly 4-articulate, 1st joint the largest, in male much more fully developed, composed of a 3-articulate ped- uncle and a well-defined, 4-articulate tlagelhun densely clothed with sensory fila- ments. Mandibles very small and feeble in structure, cutting part narrow, molar expansion forming a thin acuminate lappet armed at the tip with a few small denticles. Oral parts in male, excepting the maxillipeds, abortive, epistome form- ing a rounded projecting lobe. Chelipeds in female of normal appearance, with the hand more or less expanded, thumb generally serrated inside; those in male feebler in structure, with the hand narrower, and the fingers quite simple. 1st pair of pereiopoda not very different from the 2 succeeding pairs, the .'j posterior pairs generally more strongly built, and having the outer joints armed with spines. Pleopoda in female rather small, sometimes wanting: those in male well-developed. Tropoda. as a rule, birainous. sometimes, however, apparently simple, the outer raiuus not being distinctly defined from the basal part, rami always very unequal, the inner one much the larger and Inarticulate, the outer with either one or two articulations. Incubatory pouch normal. Ii'rHKir/,-*. This genus is chiefly characterised by the feeble structure of the mandibles. From the preceding genera it may moreover be at once distinguished by the superior antenna' in the female being distinctly -l-articiilate. not as in the former :i-articulate. The genus comprises numerous species, which on the whole are true deep-water forms and tubicolar in habits. Besides the b' Norwegian species described below, the arctic form Ty the structure of the ehelipeds and uro- poda, as also by the dentiform projection occurring on each side of the terminal segment of the metasome. The form at first recorded by the present author from the Norwegian North Atlantic Expedition as Tmurix ixltutiHctix is undoubtedly identical with Lilljeborg's species. OcciirroK-.'. The species occui's along the whole Norwegian from Chrisliaiiiafjord to Vadso in depths ranging from 31) to H>0 fathoms. 28 Distribution. -- Off Reykjavik, Iceland, and at Stat. 290 of the Norwegian North Atlantic Expedition (the present author); coast of Denmark (Meinert). 2. Leptognathia breviremis (Lilljeb.) (PL XIII, fig. 1) Tanais breviremis, Lilljeborg, 1. c. p. 21. Specific Characters. 9- Body much shorter and thicker than in the preceding species, being scarcely 6 times as long as it is broad, with the cepha- losome longer than the first 2 segments of mesosome combined, and rather nar- rowed in front. Segments of mesosome separated by rather deep, though nar- row constrictions, the 1st one not being much shorter than the 2nd. Metasome somewhat fusiform in outline, being slightly dilated in the middle, with the side- contours regularly convex, and the terminal segment evenly rounded at the tip. Superior antenna with the basal joint not attaining the length of the other 3 combined, 2nd joint fully as long as the outer 2 taken together. Chelipeds of moderate size, with the hand about the size of the carpus, and somewhat dilated beyond the middle, fingers much shorter than the palm. Pereiopoda resembling in structure those in the preceding species, except that the basal joint of the 3 posterior pairs is less tumefied. Uropoda very short, scarcely longer than the terminal segment of metasome, inner ramus biarticulate and tipped by long divergent setse, outer one extremely small, uniarticulate. Length 1.45 mm. Remarks. The present species, established by Prof. Lilljeborg, is easily distinguished from the other species belonging to this genus by its comparatively short and thick body, and by the comparatively short uropoda, which latter character lias given rise to the specific name proposed by its discoverer. It is a rather small species. Occur ence. I have met with this form rather frequently in the Chri- stiania Fjord at depths ranging from 20 to 60 fathoms, and also in several other places on the south and west coasts of Norway. It extends northwards as fai- ns Kvalo on the Nordland coast. Distribution. Bohusliin (Lilljeborg); Kattegat (Meinert). 3. Leptognathia filiformis (Lilljeb.) (PI. XIII, fig. 2). Tanais filiformis, Lilljeborg, 1. c. p. 23. '^/H'dfic Characters. 9- Body extremely slender, almost filiform, 11 times as long as it is broad, with the cephalosome rather narrow, and the 1st 29 and last segments of mesosome scarcely more than half as long as the others. Metasome slightly dilated, and scarcely longer than the last 2 segments of meso- some combined, terminal segment of medium size, and obtusely rounded at the tip. Superior antennae with the basal joint much shorter than the other 3 com- bined, 2nd joint comparatively large, equalling in length the outer 2 taken together. Chelipeds not very strong, with the hand subtriangular and about the length of the carpus. Pereiopoda comparatively small, basal joint of the 3 pos- terior pairs considerably tumefied. Uropoda attaining half the length of the metasome, inner ramus slender, Inarticulate, outer one represented only by a small knob-like projection of the basal part, carrying 2 slender seta!. Length 2.70 mm. Remarks. This form, likewise first described by Prof. Lilljeborg, is easily recognized by its extremely slender, almost filiform body, and by the apparently single-branched uropoda. Occurrence. I have met with this species occasionally in several places on the south and west coasts of Norway, from the Christiania Fjord up to Kvalo on the Nordland coast, in depths ranging from 3(3 to 100 fathoms. Distribution. Bohuslan (Lilljeborg), Oresund (Meinert). 4. Leptognathia brevimana (Lilljeborg). (1M. XIII, tig. 3). Tanais brerimamis, Lilljeborg, 1. c. p. 22. Characters. 9 Body slender and elongated, about 10 times as long as it is broad, with the cephalosome only narrowed in its most anterior part. First and last segment of mesosome about same size and shorter than the others, which are fully as long as they are broad. Metasome rather large, considerably longer than the last 2 segments of mesosome combined, and also somewhat broader, terminal segment we'll developed, occupying more than Y* f the metasome and obtusely rounded at the tip. Superior antenna of the usual structure, 2nd joint not quite as long as the outer 2 combined. Chelipeds not very large, hand shorter than the carpus, subtriangular, fingers not attaining the length of the palm. Pereiopoda comparatively small, basal joint of the 3 posterior pairs less tumefied than in L. filiformis. Uropoda about the length of the ter- minal segment of metasome, inner ramus well developed, Inarticulate, with the last joint rather short, outer ramus represented by a. rather strong, mueroniform 30 projection not denned from the basal part, and carrying outside 2 or 3 unequal setse. Length 2.80 mm. Remarks. This species was likewise established by Prof. Lilljeborg, and may easily be recogni/ed by the comparatively short hand of the chelipeds, but more especially by the peculiar structure of the uropoda. Occurrence. The species occurs along the whole Norwegian coast, from the rhristiania Fjord to Yadso. in depths ranging from 30 to 100 fathoms. Distribution. Uohuslan (Lilljeborg), Mediterranean at Messina (the present author); coast of Denmark (Meinert). 5. Leptognathia dentifera, G. 0. Sars. n. sp. (PI. XIV, ti.r. 2) Specific (..'lumtctrrx. 9- Bod}' moderately slender, being not quite 8 times as long as it is broad, ceplialosome rather narrowed in front. First free segment of niesosome somewhat longer than the last one. but considerably shorter than the other 4. Metasome ra,ther poorly developed, scarcely as long as the last 2 segments of niesosome combined, and not. any broader, terminal segment comparatively short and obtusely rounded at the tip. Superior antenme with the 2nd joint exceeding in length the outer 2 combined. Chelipeds not very strong, hand comparatively short, scarcely attaining the length of the carpus, triangular in form, with an obtuse projection in front of the insertion of the dactyl us. Pleopoda extremely small, though of normal structure, natatory seta' very short. Uropoda exceeding half the length of the metasome. basal part produced at the end inside to an intlexed hook-shaped process, both rami well defined and Inar- ticulate, the outer one scarcely half as long as the inner and much narrower. Length 1.60 mm. Iti'-iiinrh-x. This new species may be at once distinguished from any of (In- forms previously described, by the poor development of the pleopoda, but more especially by the peculiar hook-like projection issuing from the basal part of the uropoda inside, which latter character has given rise to the specific name here proposed. Occurrence. I have only seen a few female specimens of this form, some of which were ovigerous. They were taken in the Christiania Fjord at Hanko and Soon from depths of 60 100 fathoms. 31 6. Leptognathia manea, G. o. s.-n-s. (PL XIV, tio. 3). Leptognathia (?) man-ca, G. 0. Sai-s, 1. c. p. 44. Characters. 9 Body slender and elongated, more than 8 times as long as it is broad, with the segments marked off by conspicuous constrictions, posterior half slightly attenuated. Cephalosome of moderate si/e, with the side edges regularly curved. First free segment of mesosome much larger than the last one, and somewhat dilated in front. Metasome equalling in length the hist 2 segments of mesosome combined, and rather narrow, subcylindric in form, with the terminal segment short and obtuse. Superior antenna' with the 2nd joint much shorter than the outer 2 continued, ('helipeds of moderate si/e, with the hand scarcely dilated, oblong oval in form, and somewhat longer than the car- pus, fingers shorter than the palm. The 3 anterior pairs of perieopoda exactly alike both in si/e and structure, with the dactylus slender, setiform; the 3 posterior pairs having the basal joint but slightly tumefied. Pleopoda wholly absent. Uro- poda about half the length of the metasome. inner ramus Inarticulate, outer one uniarticulate and sc.arc.ely half as long. Length 2.00 mm. Remarks. The total absence (in the female) of pleopoda is a very striking feature, which at first put me in some doubt as lo the true generic relation of this form. Having, however, on a closer examination, found it to agree fairly well in all other essential characters with the species of the present genus, I prefer to retain it in the genus Leptognathia, as a, somewhat anoma- lous species. Occurrence. I have found this form in two widely separated places on the Norwegian coast, viz., in Eidsfjord, west of Listerland, and at ApehaT. Nam- dal. In both places it occurred in rather small numbers at depths of 100 150 fathoms. Gen. 5. TanaOpSlS, O. 0. Sa.s. i, ic Characters. Body comparatively robust, with the metasome unusually large and composed of (i well-defined segments. Eyes wanting. Su- perior antenna? in female distinctly 4-articulate. Oral parts very poorly developed. Mandibles extremely small, and rudimentary, unarmed, and without a trace of molar expansion. 1st pair of maxilla 1 with the masticatory lobe much curved. Maxillipeds with the masticatory lobe very short, transverse, palp slender and 32 Imt slightly setous. Chelipeds strongly built, with the basal joint very large and prominent below, carpus comparatively short and thick, hand somewhat curved and scarcely expanded in the middle. 1st pair of pereiopoda much larger tban the others. Pleopoda rather fully developed. Uropoda short, biramous. both ranii biarticulate and very unequal in size. Incubatory pouch normal. Remarks. The present new genus is founded upon the form recorded by the present author at an earlier date, as Leptognathia laticaudata, which, on a closer examination, has proved to differ very materially, especially in the struc- ture of the oral parts, from the species of that genus, and therefore ought more properly to be regarded as the type of a distinct genus. The unusually large and broad metasome together with the strongly-built chelipeds and the compar- atively robust form of the body, somewhat recall the genus Tanais; but the oral parts are very different, and the metasnme is composed of the normal num- ber of segments. The genus contains as yet but a single species. Tanaopsis latieaudata, G. 0. Sars. (PL XIV, fig. 1) Leptognathia Jnticaudata, G. O. Sars, 1. c. p. 43. Specific Characters. 9- Body linear, somewhat depressed, not much more than 6 times as long as it is broad, with the segments marked off by very narrow constrictions. (Vphalosome scarcely longer than it is broad, and consider- ably narrowed anteriorly, frontal margin subangular in the middle. The first 2 segments of rnesosome much shorter than the others, which are rectangular in shape. Metasome about half the length of mesosome, but considerably broader, being rather dilated in the middle, terminal segment well developed, pentago- nal in form, tip obtusely angular. Superior antennae about the length of the cephalosome, terminal joint rather slender equalling in length the 2 preceding ones combined. Inferior antenme with the penultimate and antepenultimate joints of the peduncle somewhat expanded and each having above a strong bristle. Chelipeds very strong, with the hand considerably longer than the carpus, and having inside a transverse row of small bristles, fingers about the length of the palm, the movable one serrated along the outer edge, the immovable one terminat- ing in 3 strong denticles. 1st pair of pereiopoda considerably longer than the others, with the propodal joint conically produced, and the dactylus very slender, setiform; the 3 posterior pairs rather strongly built, with the basal joint moderately tumefied, and the meral and carpal joints each provided inside with a single very small denticle. Uropoda not nearly attaining the length of the terminal 33 segment of metasome, inner ramus rather thick, outer scarcely half as long, and much narrower. Length 2.60 mm. Remarks. - - As stated above, this form was first described by the present author as a species of the genus Leptognathia. Having, however, subsequently had an opportunity of examining the oral parts more closely, I have found it necessary to separate it generically. It is easily distinguished from the other Norwegian Tanaids by the strongly dilated metasome and the peculiarly rigid appearance of the chelipeds. Occurrence.. I have met with this form in a few places on the south coast of Norway (Fredriksveern, Nevlunghavn, Mserdo) in comparatively shallow water, the depth ranging from 6 to 20 fathoms. Distribution. Mediterranean at Naples and Messina (the present author). Gen. 6. CryptOCOpe, G. 0. Sars, 1880. Generic Characters. Body more or less robust, with the cephalosome considerably narrowed anteriorly, front truncated. Metasome scarcely broader than the mesosome, and composed of 6 well-defined segments. Eyes wanting. Superior antennae in female short, 4-articulate, in male much larger and of a structure similar to that in the genus Leptognathia. Mandibles well developed, with the cutting edge coarsely dentated, and having on the right mandible a rather large secondary lamella, molar expansion well defined, conic or lamellar. Chelipeds rather strong and of a similar structure in the two sexes. Pereiopoda slender, especially the 3 anterior pairs. Pleopoda in female very small and rudimentary, with the rami extremely small, lobular; those in male well developed, natatory. Uropoda in female short, biramose, rami very unequal; those in male much more fully developed. Incubatory pouch formed only by 2 lamella issuing from the bases of the 4th pair of pereiopoda. Remarks. This genus is chiefly characterized by the rudimentary con- dition of the pleopoda in the female. In the structure of the other appendages it exhibits a close affinity to the genus Leptognathia', but the structure of the mandibles is slightly different, and the incubatory pouch is constructed as in the genus Tanais. Besides the Norwegian species described below, the form at first recorded by the present author as Tanais Voringii belongs to this genus. More- over, Dr. Hansen has described a third species from the Kara Sea as (..'. arct'tca. 5 Crustacea. 34 Cryptocope abbreviata, G-. 0. Sars. (PL XV, fig. 1). Tanais abbreviatus, G. O. Sars, Beretning om en i Sommeren 1865 foretagen zool. Eeise, p. 41. Specific Characters. - 9 Body extremely short and stout, sub-depressed, scarcely more than 3 times as long as it is broad. Cephalosome scarcely as long as it is broad posteriorly, and considerably narrowed in front, frontal mar- gin slightly Insinuate, with the lateral corners somewhat produced. Fifth and 6th segments of mesosome somewhat larger than the other 4, which are very short. Metasorne but little longer than the last 2 segments of mesosome combined, and gradually narrowed in its posterior part, terminal segment comparatively short and obtusely produced at the tip. Superior antennae somewhat shorter than the cephalosorne, basal joint about the length of the other 3 combined. Chelipeds rather strong, carpus comparatively short and thick, hand longer than the former, and slightly narrowed distally, fingers about the length of the palm. The 3 anterior pairs of pereiopoda rather slender, with the dactylus long and setiform; the 3 posterior pairs somewhat stronger, but with the basal joint not much tumefied. Pleopoda with the rarni quite smooth, the inner one extremely minute, nodiform. TJropoda scarcely attaining the length of the terminal segment of metasome, inner ramus distinctly biarticulate, and tipped with long diverging seta3, outer one extremely minute and uniarticulate. Length 1,40 mm. Remarks. This form may be easily recognized from the other Norwegian Tanaids by its extremely short and thick body, and by the rudimentary condition of the pleopoda. It differs from Cryptoeope arctica Hansen. which it somewhat resembles in the form of the body, in the rami of the pleopoda being quite smooth, whereas in the last-named species, according to Dr. Hansen, they are tipped with small bristles. Occurrence. I first discovered this form in the Christiania Fjord at a depth of about 30 fathoms, and have subsequently found it occasionally in other places also, both on the south and west coasts of Norway. It has not been recorded by any other author. Gen. 7. HaplOCOpe, G. 0. Sars, 1880. Generic Characters. - - 9- Body slender and elongated, resembling, as regards its outward appearance, some species of the genus Leptognathia. Metasome rather 35 narrow, sublinear, with all the segments well defined. Eyes wanting. Superior antennae (in female) distinctly 4-articulate. Mandibles well developed, and resem- bling in structure those in the genus Typhlotanais, the molar expansion being rather strong, cylindric, and armed at the tip with dentiform tubercles. Cheli- peds comparatively small, with the hand scarcely dilated. The first 3 pairs of pereiopoda of similar structure, and more slender than the 3 posterior. Pleopoda (in female) imperfectly developed, forming simple oval lamellae, without a trace of seta). Uropoda rather slender, biramous, rami unequal, Inarticulate. Incuba- tory pouch normal. Remarks. The most prominent character of this genus is the simple structure of the pleopoda in the female, and it is indeed from this character, that the generic name has been derived. In outward appearance, as also in the structure of the several appendages, it exhibits a close resemblance to the genus Leptognathia ; but the structure of the mandibles is very different, and agrees much more closely with that found in the genus Typhlotanais. The genus con- tains as yet but a single species. Haplocope angusta, G. 0. Sars. (PI. XV. fig. 2). Haplocope anyusta, G. 0. Sars. 1. c. p. 51. Specific Characters. 9- Body extremely slender and narrow, being fully 10 times as long as it is broad. Cephalosome rather small, slightly nar- rowed anteriorly, front truncated. 1st free segment of mesosome but little smaller than the next succeeding ones and somewhat dilated in front, last segment the smallest. Metasome about the length of the last 2 segments of mesosome combined, and nearly of uniform breadth throughout, terminal segment of medium size, and angularly produced in the middle. Superior antenna) somewhat shorter than the cephalosome, basal joint only attaining the length of the 2 succeeding joints combined, last joint narrow, conic. Chelipeds rather small, hand about the length of -the carpus, fingers shorter than the palm. 1st pair of pereiopoda scarcely longer than the 2 succeeding pairs; the 3 posterior pairs a little stronger, and having the outer joints spinotis. Uropoda about half the length of the me- tasome, inner ramus rather elongated, outer scarcely more than half as long and much narrower. Length 1.70 mm. Remark*. As stated above, this is the only species as yet known of the genus, and may easily be recognized by its slender, narrow body, and the simple, lamelliform pleopoda, Occurrence. I have met with this form occasionally in 3 widely remote localities, viz., in Eidsfjorcl, west of Listerland, at Bekkervig, on the west coast of Norway, and at Apelveer in Namdal. In all 3 places it occurred in rather small numbers together with other Tanaids, in depths ranging from 100 to 150 fathoms. Gen. 8. StrOIlgylUra, G. O. Sars. Generic Characters. Body more or less elongated, subcylindric in form, with rather hard integuments. Cephalosome comparatively large, narrowly trun- cated in front. Metasome of quite an unusual size, cylindric, slightly widening behind, and composed of 6 well-defined segments, the last of which is very large, cupuliform. Eyes wanting. Superior antennae in female rather strong, 4-articu- late. Mandibles well developed, cutting part strongly incurved, and divided into a few short teeth, molar expansion large, laminar, minutely dentated at the tip. Chelipeds strongly built, with the hand rather large. Pereiopoda comparatively slender and elongated, with the dactylus narrow, setiform. Pleopoda in female wholly absent. Uropoda very small, though distinctly biramous. Remarks. The present genus is prominently distinguished by the peculiar appearance, in the female, of the nietasome, which is of quite an unusual size, and has the segments perfectly cylindric, without a trace of epimera. Nor is the slightest rudiment of pleopoda to be detected in the female, whereas in the male they seem to occur in the normal condition. In addition to the type species described below, Messrs. Norman & Stebbing have recorded -another species, 8. arctophylax, from the Porcupine Expedition. Strongylura cylindrata, G. 0. Sars. (PI. XVI, fig. 1). Strongylura cylindrata, G-. O. Sars, 1. c. p. 53. ific Characters. 9- Body rather slender and narrow, about 9 times ;is lung ;is it is broad, and slightly narrowed in the middle, with the segments marked off by conspicuous constrictions. Cephalosome comparatively large, almost equalling in length the first 3 segments of mesosome combined, oblong oval in I'orin, jind slightly narrowed in front. 1st free segment of mesosome much shorter than the others. Metasome occupying rather more than l / s of the length of the 37 body, or equalling about the first 5 segments of mesosome combined, slightly widening behind, terminal segment large, oblong oval and very smooth, tip obtusely rounded. Superior antennae almost attaining the length of the cephalosome, basal joint about the length of the other 3 combined, terminal joint comparatively short and obtusely blunted at the tip. Chelipeds rather strong, hand oblong oval and longer than the carpus, lingers shorter than the palm, the immovable one minutely serrulate inside. The 3 posterior pairs of pereiopoda considerably more strongly built than the 3 anterior ones, and having the outer joints armed with ciliated spines, basal joint remarkably constricted at the base. TJropoda very short, inner ramus conical, biarticulate, and tipped by long diverging setse, outer ranius extremely minute, tuberculiform, though well defined from the basal part. Length 2.85 mm. Remarks. From 8. ardophtjlcu' of Norman & Stebbing. the Norwegian species may be at once distinguished by its much more elongated body and the com- paratively larger size of the metasome. A few specimens, however, are of con- siderably shorter form, but as in all of these there are distinct traces of pleo- poda, they are, I believe, of the male sex, though probably not yet sexually mature. Occurrence. I have found this peculiar Tanaid in several places, both on the south and west coasts of Norway, in depths ranging from 50 to 200 fa- thoms. It extends northwards to Selsovig, situated just within the polar circle. Gen. 9. Anarthrura, G. o. Sars, isso. Generic Characters. Body elongated, subdepressed, with rather thin, semipellucid integuments. Cephalosome comparatively short and obtusely trun- cated in front. Metasome in female very poorly developed, narrower than the mesosome, and without a trace of segmentation; that in male, however, of quite normal appearance, being divided into 6 well-defined segments. Eyes wanting. Superior antennge in female 4-articulate, in male but slightly different, though composed of 5 articulations. Mandibles extremely small and rudimentary, cutting edge simple, molar expansion wanting. Chelipeds comparatively small, with the basal part of a somewhat unusual structure, being oval, tumid, and divided into 2 distinct segments, hand rather small, with the palm unusually short. The 3 anterior pairs of pereiopoda rather slender and nearly equal, the 3 posterior pairs rather different, and considerably more strongly built. Pleopoda in female 38 wholly absent, in male normally developed. Uropoda imperfectly biramous, the outer ramus not being denned from the basal part. RemarTcs. In this genus also, the structure of the metasome in the female yields the most conspicuous distinctive character; but whereas in the. genus Strong i/lura this division is of quite an unusual size, it is in the present genus more reduced in size than in any hitherto known Tanaid. In the male, however, this part exhibits quite a normal appearance. The structure of the chelipeds is likewise somewhat peculiar and differs, among other things, from that of all other Tanaids in the form of the basal part. The oral parts, and especially the mandibles, exhibit a similar rudimentary condition to that found in the genus Tanaopsis. Besides the typical species described below, the Austra- lian form Parattuuii* ////mm- Haswell, according to the opinion of the Rev. Mr. Stebbing, should more properly be referred to this genus. Anarthrura simplex, G. 0. Sars. (PI. XVI, fig. 2). Anarthrura sinqrtex, G. 0. Sai-s, 1. c. p. 54. Specific Characters. Body in female about 8 times as long as it is broad, in male somewhat shorter, segments marked off by rather deep constrictions. Cephalosome distinctly depressed, scarcely longer than it is broad, and obtusely truncated in front. 1st and last segments of niesosome shorter than the others, and almost quadrate in outline. Metasome in female scarcely longer than the penultimate segment of mesosome, narrow cylindric, or very slightly depressed, and somewhat constricted in the middle, tip obtusely angular; that in male nearly twice as large, and of altogether normal appearance. Superior antenna? in female about the length of the cephalosome, basal joint but little longer than the 2 succeeding ones combined, terminal joint narrow, conical in form. Chelipeds with the basal part occupying half their length, and having its first segment much larger than the 2nd. hand longer than the carpus, but rather feeble, with the palm unusually short, fingers narrow and not perfectly contiguous when shut, the movable one slightly serrated outside, the immovable one nearly straight and termin- ating in a lanceolate point. The 3 anterior pairs of pereiopoda exactly alike, having the propodal joint tapering conically, and the dactylus long and setiform; the 3 posterior pairs more strongly built, with the basal joint rather tumefied, and the dactylus quite short. Uropoda generally turned obliquely outwards, inner ramus well defined. Inarticulate, outer represented by a conical, setiferous pro- jection of the basal part. Length of female 2.35 mm. Apseudidse. I s opo da. PI. i r^- t --.-( y^^sm fcSX -^"t -2$&?8Gm G.O. S ars, autogr. Apseudes spinosus, (M.Sars). Apseudidee. I s op o da. P!.H G.O. S ars, autogr . Apseudes spinosus.fM. Bars), (continued.) Ta na i d SB. I s op o da- pi, v. G 0. S ars, autogr. Tanais tomentosus, Kroyer. Ta na i d ae. I s op o da.. PI. VI I "V F > 6.0. S ars, autogr. Heterotanais J3rsiedi, (Kr_yer), Ta n a \ d SB . I s opo da- VII. G.C. S ars, autogr. Paratanais Batei, G.O.Sars. Jar. aid se. I s op o da- i. VIII G.O. S ars, autogr. i. lyphlotanais tenuimanus,(Lilljeb.) micro chains, G. O.Sars Ta n a i d I s op o da- I. IX. m ' 51 '$i&k**ii ' -/ ^ G-O. S ars, autogr Typhlotanais finmarchicus, G. 0. Sars. Ta n a i d ae. ! s opo da. Pl.X. N G. 0. S ars, autogr . 1. Typfilptsnis aaq.virem is,(Lilljeb). 2. assimilis, G.O.Sars. 3. tenuicornis.G.O. Sars Ta n a i d as I s op o da.. PI. XI. G.O. S ars, autogr . I.Typhlotanais brevicornis, (Lilljeb). cornutus, G.O. Sars. 3 ,, penicillatus, G.O.Sars. Ta naid as. I s op o hy the present author as Paranthura tenuis, and subsequently referred by him to the genus Ptilnuthura of Harger. On a closer examination, I have, however, found it necessary to separate this form also from the above-named genus, on account of some apparently very essential differences. Messrs. Norman & k.tebbing retain it in the genus Paranthtna : but this seems to me inadmissible, as it ex- hibits several very marked differences from that genus, both in the structure of the oral parts and in that of the other appendages. The structure of the 1st p:iir of legs in this genus is rather remarkable from the circumstance that it ex- hibits a very pronounced approach to a chelate character, like that found in the Tanaidse. Leptanthura tenuis, G. 0. Sars. (PI. XX.) I'nrrnilhnra tennis. 1 ) G. 0. Sars, Bidrag til Kundskaben om Dyrelivet pa a vove Havbanker. Ohr. Vid. Selsk. Forh. 1872, p. 89. Specific Characters. Body, especially in male, exceedingly slender, almost filiform, with all the segments very sharply defined. Cephalon about half the size of the 1st segment of mesosome and scarcely narrower, almost quadrate in out- line, frontal margin slightly bi-sinuate. The first 2 segments of mesosome and Ilie last of about equal size, the 4 others somewhat longer, being more than twice as long as they are broad; dorsal face of all segments perfectly smooth. .Met;isome. including the telson. in female about the length of the last 2 segments ot mesosome combined, in male considerably longer, somewhat fusiform in shape, J ) J'. Icnin* of Harger, established some years afterwards, is a very different species, not belonging to the same genus. 49 being conspicuously constricted at the base of the caudal fan, all segments very sharply defined, and having distinct rounded epimera. Superior antennae in female much shorter than the cephalon, first joint of the peduncle about the length of the other 2 combined, flagellum not exceeding in length the last peduncular joint, conic in form, and exhibiting 1 or 2 extremely small terminal joints; those in male more than twice as large, and, as a rule, refiexed, last joint of the peduncle very movably articulated to the 2nd, and gradually widening dislally, fiagellmn fully as long as the peduncle, and rather thick at the base, being composed of about 10 articulations, each provided with a dense whorl of long sensory filaments, whereby the outer part of the antenna acquires a brush-like appearance. Inferior antenme of same structure in the two sexes, rather stout, flagellum very small, with 3 4 extremely minute terminal joints, carrying a dense brush of bristles. 1st pair of legs likewise of a similar appearance in the two sexes, propodos large, * oval, set obliquely on the short carpus, palm deeply concave, and armed with a row of flattened denticles, thumb-like process very prominent. The 2 succeed- ing pairs of legs with the propodos in female comparatively short, subquadrangular, palm defined below by a distinct angle, that in male much longer, pyriform, palm occupying the whole lower edge. First pair of pleopoda having the outer plate oblong oval, gradually widening distally. Uropoda with the inner ramus rather narrow, and reaching considerably beyond the telson, terminal joint about the length of the proximal one. and having at the tip a dense brush of slender bristles, outer ramus broadly c:jrdiform, arching over the base of the telson. so as almost to meet the corresponding ramus on the other side in the middle, edge smooth, only clothed with scattered bristles. Telson in male broad, scarcely more than twice as long as it is broad, in female considerably narrower, edges smooth, except at the tip, which carries 2 long and 2 short bristles. Colour a pure white. Length of female 7 mm., of male H'/o mm. Remarks. By its extremely slender, filiform body, this form is easily re- cognized from most other Anthuridce, though the species of Antht'litra and Hijsstn'n in this respect would seem to approach it. On account of its pure white colour and comparatively small size, it may at first sight be mistaken for a Tanaid. Oci.-iirrenee. I first detected this form at Hvitingso, outside Stavanger. in a depth of 150 200 fathoms, and have subsequently taken it in the inner part of the Stavanger Fjord at Jelse, as also rather plentifully in the Trondhjem Fjord in similar depths. It is a rather sluggish animal, creeping slowly along the bottom. At times it is seen to bend its body almost in a circle ; but I have never seen it make any attempt to swim, though the structure of the pleopoda seems to admit of such a motion, at least in the male sex. Distribution. -Stat. 22 of the Porcupine Expedition, located off Lisbon (Norm. & Stebbing). 7 Crustacea. 50 Fam. 2. Gnathiidae. r*. Body of male and female of very different appearance, being. in the former, depressed and dilated in front, in the latter, more or less fusiform ; body of immature animal (larva) also rather different, though more resembling that of female. Cephalon of male very large, as compared with that of female and larva. Mesosomc apparently composed of only 5 segments, though a rudi- mentary anterior and posterior segment may he discerned. Metasome narrowing ahruptly to a width much narrower than the mesosome, composed of 6 segments, the last triangularly produced hehind, and forming together with the uropoda a nor- mal caudal fan. Antennae comparatively short, and of same structure in the two sexes, issuing close together from the outer corners of the cephalon. Oral parts in the adult animal much reduced, consisting in the male of a pair of mandibles freely projecting in front and a pair of peculiarly modi- fied maxillipeds, in female of only the latter appendages. Oral parts in the larva present in the normal numher, and densely crowded together, to form an apparatus for penetration and suction. Gnathopoda in male valve-like, arching over the lower face of the cephalon, in female much smaller and more distinctly segmented, in the larva pediform, terminating in a strong hook. Only 5 pairs of pereiopoda present, the last pair being absent. Pleopoda of equal structure, natatory or exclusively respiratory (in the adult animal). No true incubatory pouch present, the ova undergoing their development within the dilated body-cavity. Remarks. This is one of the most anomalous families of the order, and in some points even differs more pronouncedly from the typical Isopoda, than do the Alwinl'ula' and Tanaidce. The sexual differences are highly remarkable, and the not yet mature animals differ also so widely from the adults, that they have long been referred to quite a separate family, Prmuzulfe. The latter lead a true parasitic existence, as shown by the peculiarly modified oral parts, whereas the adults are scarcely at all parasitic. The complete absence of the last pair of pe- reiopoda affords another very anomalous character, not found in other Isopoda, except in the recently hatched young. The family comprises as yet but a single genus, Gnatltia Leach; but it is most probable, that it will be found appropriate to subdivide this genus into several distinct genera, as there are some apparently essential differences to be found on comparing the several species. Indeed, the Rev. Mr. Stebbing has re- cently proposed to raise a most anomalous form described by Mr. Beddard from Hie Challenger Expedition, to the rank of a distinct genus Euneoyttathitt. and he 51 has advanced the opinion that another species, established by the same author from a fragment of a specimen, may also require to be transferred to a new genus. Gen. GnatMa, Leach, 1814. Syn: Anceus, Eis.su (male). ,. Praniza, Latr. (larva). Generic Characters. Body in male subdepressed, and more or less di- lated in front, with the cephalon very large, subquadrangular, and flattened ante- riorly, inesosome divided by a more or less conspicuous constriction into 2 sections, the anterior comprising 2, the posterior 3 well-developed segments, the foremost rudimentary segment being consolidated with the head, the hindmost received between the projecting lateral parts of the 5th segment. Body in female and larva more or less fusiform, with the cephalon rather small, and some of the segments of mesosome fused together. Metasome in both sexes, as also in the larva, much narrower than the mesosome, sublinear in form. Eyes, when present, placed laterally. Antennas comparatively short and subequal in length, both pairs with distinctly denned flagella. Mandibles in male of different form ind the different species, more or less flattened, forceps-like. Maxillipeds without epignaths, masticatory lobe simple, palp consisting of 4 flattened joints fringed outside with strong plumose seta. 1 ; those in female much smaller, but of a similar structure. Oral parts in the larva combined into a rostrum-like cone projecting in front, and in a great measure styliform. Gnathopoda in male forming a pair of very large curved plates arching over the lower face of the cephalon, and terminating in a small apical joint; those in female much smaller and more pediform, being divided into 3 or 4 joints, and having at the base a thin lamella. IVreiopoda subeqiial and of normal structure. Pleopoda with the rami uni-articulate, tipped with long seta 1 , or quite, naked (in the adult animal). Uropoda with both rami lamelliform, snhe- qual, and edged with slender bristles. Remarks. This genus was established as early as in the year 1814 by Leach under the above name, which, according to the rules of priority, must be preferred to the more generally used terms Anceus (the male) and /'ranita (the larva). To the French zoologist, E. Hesse, is due the merit of first having made out precisely the true relationship between the male, female, and larva, which had not formerly been fully recognized, though Leach had already conjectured, that the 52 Praniza might be the female of Anceus. Indeed, the 3 forms are so widely diffe- rent both in their general appearance, and in the structure of some of the appen- dages, that one ma} 7 be easily led to suppose that they belonged to as many distinct genera. The communications of M. Hesse therefore at first occasioned no little discussion among Corcinologists, and the correctness of his observations relating to the transformation of Praniza, into Ancen*. \v;is even simply denied 1 ); but subsequent investigations have, on the whole, fully confirmed his statements about the peculiar trimorphism occurring in tins genus. A rather large number of species, amounting to more than 20 in all, have been recorded from different parts of the Oceans; but the far greater part of them have been only described from male specimens. To the fauna of Norway belong 4 species, to be described below. l. Gnathia maxillaris (Mont,). (PL XXI, PI. XXII, fig. 1.) Cancer nHt.rUh'tris, Montague, Trans. Linn. Soc., Vol. VII, p. 65, PI. 6, fig. 2. Syn: Anceus maxittaris, Lamk. cf. Praniza coeruleata, Desm. (Larva). Anceus oxyurceus, Lilljeb. cf- Praniza Edwardii, Sp. Bate 9- ? Anceus iiHiiitirni us. Hesse. ., Specific Characters. Mali'. Body almost elavate in shape, being gradually expanded in front, with the anterior part of inesosorne divided from the posterior by a rather deep constriction. Cephalosome transversely quadrate, deeply ex- cavated above in its anterior part, dorsal face smooth and distinctly areolated, supra- ocular denticle comparatively small. Posterior division of mesosome narrower than the anterior, dorsal face quite smooth, without any areolation. Eyes well developed. Mandibles rather large, broadly lanceolate, with a slight obtuse notch outside, inner edge bulging in the middle, and obscurely crenulated in its outer part, tip scarcely incurved. Pereiopoda with scattered tubercles inside the outer joints. Pleopoda well developed, natatory. Uropoda with the rami foliaceoiis. and fringed with long ciliated setie. Terminal segment of metasome triangular, gradually tapering to a point carrying 2 slender bristles. Sexual tubercle small. but little prominent. Colour yellowish brown, with the areohe of the head whitish, defined by narrow dark brovMi grooves. Female: Body oblong fusiform, with the 2 ') It may be noted that tin; strange controversy which at first took place between M. Hesse and Mr. Sp. Bate, was merely due to the fact that the latter author regarded the adult female as a Praniza, whereas M. Hesse more correctly named it p, female 53 posterior pedigerous segments coalesced. Cephalosome obtusely produced in front, being fully as long as it is broad at the base. Pleopoda, as in male, natatory. Body whitish, mottled all over with reddish brown specks. Length of male 5 mm., of female about the same. Remarks. The identification of this form with Montagu's species is some- what doubtful; but as, at least off the coasts of Norway, it is by far the most common species, I am much inclined to believe, that it is the form originally de- scribed as Cancer maxillaris. The form recorded by Sp. Bate & Westwood under this name is a very different species, showing in some respects a closer relation- ship to the following species, though apparently specifically distinct. The pre- sent species may be easily distinguished in both sexes from the 3 other Norwegian species, the male especially being readily recognized by the very large lanceolate mandibles, and by the very pronounced areolation of the dorsal face of the head, the female, by the form of the cephalosome. Occurrence. I have met with this form rather abundantly along the whole south and west coasts of Norway, from the Christiania Fjord up to the Lofoten Islands, in depths varying from 20 to 100 fathoms, and generally on muddy bottom, Male specimens are much more frequent than female ones, both being always found slowly creeping on the bottom. The larvae (Praniza) are much more agile, and are often seen swimming about with great speed. Occasionally I have found them clinging to the skin of living fishes of various kinds, when just brought up by the fishing-line. Tn such cases, the posterior part of the mesosome generally forms a greatly swollen, unse<:iiieiited division (see PI. XXII, fig. 1) tilled with the blood of their hosts, and this is, OH the whole, invariably the case with more advanced larvae, even when taken up by the dredge. In all probability, they all lead a true parasitic existence, but being well fitted for swimming, they may at times leave their hosts. I have once witnessed the transformation of a Pranlza (larva) into the adult male form (Awe/is). Immediately after the transformation, the integu- ments of the animal were still rather soft, semipellucid, and mottled all over with reddish brown specks, as in the larva, without as yet showing the distinct areolation of the dorsal face of the head, which distinguishes the fully grown male. Dimtrilnftion. British Isles (Mont.), Kattegat (Meinert), coast of France (Hesse). 54 2. Gnathia dentata, G-. 0. Sars. (PI. XXII. fig. 2.) dentatus, G. O. Sars, Umlersegelser oyer Hardangerfjordens Fauna I. Chr. Vid. Selsk. Forh. 1871, p. 32. Specific Characters. Male: Body comparatively more elongated than in (1. nui.rUlaris. and less clavate in form, with the posterior division of mesosome scairt-ly narrower than the anterior, both being defined by a very conspicuous constriction. Cephalosome rounded quadrangular, with the supra-ocular processes rather prominent, dorsal face, behind the anterior excavation, evenly convex, without any areolation, but, like the first 2 segments of mesosome, clothed all over with very small spikes and stiff hairs. Posterior division of mesosome quite smooth, middle segment divided dorsally into 2 areolse, separated by a rather broad membranous space. Metasome comparatively shorter and broader than in G. maxillaris, with the epimera triangularly produced. Eyes well developed. Inferior antennae with the last joint of the peduncle rather large, subfusiform. Mandibles much smaller than in G, ma.r/Unris, with a very conspicuous tooth-like projection in the middle of the outer edge, tip slightly incurved, acuminate, inner edge distinctly crenu- lated, and obtusely produced near the base. Pereiopoda without any distinct tubercles inside the outer joints. Pleopoda well developed, natatory. Terminal segment of meta- some triangular and rather broad. Uropoda with the rami well-developed, foliaceous. Sexual process very long, pointing anteriorly. Colour greyish white.- Female: Body rather narrow with the 3 posterior pedigerous segments completely coalesced, and forming together an oblong, subcylindric division, more than 4 times as long as that preceding it. Cephalosome very small, twice as broad as it is long, front hut very slightly produced, minutely bidentate at the tip. Pleopoda, as in the male, natatory. Colour yellowish white, mottled with scattered reddish specks. Length in both sexes 4 mm. Remarks. The present species may be easily distinguished from the pre- ceding one, in the adult state of both sexes, whereas the larvse are of a very similar appearance to those of G. ma,r'iUr'ts. In the male, the structure of the mandibles and the non-areolated dorsal face of the head may serve as easily recognizable distinguishing marks; in the female, the very different shape of the Cephalosome, and the complete fusion of the posterior dilated segments of the mesosome. Occurrence. This form was first observed by the present author in the inner part of the Hardanger Fjord, and has subsequently been found occasionally in .-i few other places on the west coast of Norway, as also in the Trondhjem Kjord. It generally occurs on a stony bottom among Hydroida, the depth vary- ing from 20 to 50 fathoms. In habits it exactly agrees with the type species. 55 3. Gnathia elongata, Kniyer. (PI. XXIII, fig. 1.) Anceus elongatus, Kroyer, Nat. Tidsskr. Ny Rsekke, Bd. II, p. 388. Specific Characters. Male: Body rather elongated, with the mesosome of nearly uniform breadth throughout, and the median constriction not very much pronounced. Cephalosome of moderate size, rounded quadrangular, with the supra- ocular processes well -defined. Dorsal face of both cephalosome and mesosome very uneven, with irregular depressions, and clothed .-ill over with minute spinules and short hairs. Penultimate pedigerous segment divided dorsally by a narrow longitudinal groove into 2 halves. Metasome comparatively narrow, and scarcely longer than the 2 posterior pedigerous segments combined, epimera small. Eyes well-developed, though not very large. Mandibles comparatively small, with only a very slight notch outside, inner edge obtusely produced in the middle, tip acute, slightly incurved. Pereiopoda with small tubercles inside the outer joints. Ter- I minal segment of metasome considerably narrowed in its outer part, which is conical in shape. Uropoda with the rami comparatively narrow. Female: Body much broader than in male, with the last 3 pedigerous segments well-defined, and together forming an oblong oval division about 3 times as long as that preceding it. Cephalosome with the frontal part slightly produced and bidentate at the tip. Pleopoda in both sexes with the rami quite smooth forming narrow site-like plates not fitted for swimming, but apparently respiratory in character. Colour of male greyish white, with a light bluish tinge, of female, yellowish, seniipellucid, with scattered brown dots. Length in both sexes 4 mm. Remarks. This form was first described by Kroyer from male specimens collected off the Greenland coast, and was subsequently figured in (laimard's great work. The female, however, has hitherto been unknown. Both sexes are easily distinguishable from those of the other Norwegian species. The immature form (Praniza), however, looks very like that of the 2 preceding species. Occurrence. Along the whole Finmark coast, this arctic form is not infre- guently met with. In the harbour of Hammerfest especially, 1 have taken it in great abundance at a depth of from 20 to 40 fathoms, both sexes occurring in nearly equal numbers, and in the same place, larva? (the Prani/a-form) were also found rather plentifully. It extends southwards to the Lofoten Islands; farther south, I have never met with it. The adult animal is very sluggish in habit, the structure of the pleopoda, indeed, showing it to be quite unable to swim. The larva?, on the other hand, move through the water with great agility, and most probably, at times, lead a parasitic life on the skin of various fishes. 56 Distribution. Greenland (Kroyer), the Kara Sea (Hansen), St. 223 & 290 of the Norwegian North Atlantic Expedition. 4. Gnathia abyssorum, G. 0. Sars. (PL XXIII, fig. 2.) J// and a half times as long as that preceding it. Cephalosome triangular, front rather produced, and bi- dentate at the tip. Pleopoda in both sexes not natatory, rami narrow sacciform, the outer one considerably shorter than the inner. Colour of male bluish white, of female whitish pellucid, without pigmentary spots. Length in both sexes about 3 mm. Remarks. This form was at hrst observed by the present author only in the female sex; but subsequently I have also succeeded in finding the male, and am thus enabled to draw up a complete diagnosis of the species. The dis- covery of the male has shown this species to be very nearly allied to the form described by the present author from the Norwegian North Atlantic Expedition as , Imv/f.-,- /vy/^.s7/rs'.- but the present species is of much inferior size, and of a '-till shorter and more compact form, differing, moreover, in the shape of the mandibles, and in the larger size of the eyes. By the 2 latter characters, it is also easily distinguishable from the 3 other Norwegian species. Occurrence. A single female specimen of this form was first taken in the inner part of the Hardanger Fjord, at Utne. from the considerable depth of 57 200 fathoms. Some years afterwards, I met with this species in a widely distant locality, viz., at Hasvig, West Finmark, where a few specimens, males and fe- males, were taken from depths of from 150 to 200 fathoms. Fam. 3. /Egidae. Characters. --Bo Ay more or less broad, depressed, with the dorsal face evenly vaulted and very smooth. Gephalon comparatively small, transverse, front 7iot produced above the bases of the antennae. Segments of mesosome well-defined and closely crowded together, all, excepting the 1st, having distinct coxal plates firmly connected with them laterally. Metasome composed of 6 well-defined seg- ments, the last large, scutiform, and ciliated at the edges, constituting together with the uropoda a well-developed caudal fan. Eyes, when present, large, extend- ing more or less over the dorsal face of the head. Antennae pointing laterally, the superior ones shorter than the inferior, and originating close together in front of them; both pairs provided with distinctly-defined, multiarti dilate flagella. Oral parts of rather anomalous structure, being modified for piercing and tearing the skin of other animals. The first 3 pairs of legs short and thick, prehensile, ter- minating in a strongly curved, hook-like dactyl us, the 4 posterior pairs more slen- der, and ambulatory in character. Pleopoda with the rami large, foliaceous, cili- ated at the edges, serving partly for swimming, partly for respiration. Uropoda attached laterally beneath the base of the terminal segment, and having the rami of coarser structure, and partly fringed with spines. Sexual difference not very pronounced. Remarks. This is one of the 6 families comprised within the large group Cymothoidce, and is chiefly distinguished from the other families by the com- paratively broad, flattened body, and by the structure of the antenna; and oral parts. All the forms belonging to this family lead a pnrasitic existence, being generally found clinging to the skin of fishes of different kinds, though they arc pretty well adapted for moving freely about by the aid of the largely developed pleopoda. Four or 5 genera are comprised within this family, 3 of which are represented in the fauna of Norway. 8 Crustacea. 58 Gen. 1. ^Ega, Leach, 1815. Generic diameters. Body rather compact, with very hard integuments, and the segments of mesosome nearly equal in size, the 4 posterior ones generally having a line running across them dorsally. Coxal plates thick, sculp- tured outside with 2 curved ridges, and produced posteriorly to an acute point. Metasome not much narrower than the mesosome, its 5 anterior segments very short, and having the epimera acutely produced. Eyes large, reniform, sometimes approaching dorsally, so as to meet in the middle. Superior antennas rather short, with the first 2 peduncular joints more or less expanded. Anterior lip having in front a smooth linguiform plate (epistome) projecting between the bases of the inferior antennae. Posterior lip terminating in 2 comparatively small, lanceolate lappets. Mandibles having at the base outside a well-developed 3-articulate palp, inner part of the body greatly produced, and terminating in a sharpened, knife-shaped cutting edge, molar expansion wanting. Anterior maxilla? with only a single narrrow masticatory lobe tipped by short spines. Posterior maxilla? broader, sub- lamellar, terminating in 2 unequal lobes armed with recurved denticles. Maxilli- peds rather strong, epignath confluent with the basal part, masticatory lobe rudi- mentary, terminal part (palp) 5-articulate, incurved, subtortuous, and armed with strong recurved denticles. Anterior pairs of legs with the propodos simple cylind- ric, not expanded, dactylus abruptly curved in the middle, and terminating in a very acute point; the 4 posterior pairs successively increasing in length, with the propodal joint short, and the dactylus comparatively small. Uropoda with the basal part produced at the inner corner to a narrow lanceolate process. Remarks. This genus was established as early as in the year 1815 by Leach, and represents the type of the family ^Ey'idce. It is chiefly distinguished from the other 3 genera represented in the Norwegian fauna, by the compara- tively broad metasome, the large reniform eyes, the structure of the antenna? and that of the mandibles and maxillipecls. Moreover, some differences are found in the structure of the legs. The yEga? comprise some of the largest known Iso- poda, and are well known by our fisher-men by their frequent occurrence on the skin of fishes of various kinds. They are generally named here in Norway 'Fisk-Bjorn", that is, fish-bear. The genus comprises rather a large number of species from different parts of the Oceans, amounting to more than 20 in all. To the fauna of Norway belong 7 species, to be described below. 59 1. >ga psora (Lin.). (PI. XXIV.) Oniscus psora, Linne, Fauna svecica, ed. II, 17H1. Syn: ^Ega emaryinata, Leach. Specific Characters. Body rather broad, oval in form, about twice as long as it is broad, with the dorsal face but slightly vaulted, and very smooth and polished; transverse lines of the 4 posterior pedigerous segments indistinct. Ce- phalon with the front slightly produced in the middle. Coxal plates of moderate size. Metasome about half the length of the mesosome, epimera well- developed and pointed. Terminal segment triangular, pointed at the tip, dorsal face smooth. Eyes subreniform, separated in the middle by a distinct, though rather small interspace. Superior antenna? with the first 2 peduncular joints rather broad, the 2nd being produced at the end anteriorly to a hood-like projection curving over the succeeding joint, liagellum about half the length of the peduncle. In- ferior antenna? nearly twice as long as the superior, with the rlagellum somewhat longer than the peduncle. 1st pair of legs with only 2 blunt spines at the end of the meral joint inside, the 2 succeeding pairs with a row of from 7 to 8 si- milar spines on the same joint; the 4 posterior pairs with the outer part densely clothed with short spines. Uropoda with the inner plate deeply emarginated near the end, outside, outer plate oblong, with about 12 short spines along tin- exterior edge. Colour light reddish brown. Length of adult animal reaching to 50 mm. Ji'emarJcs. This is the species first recorded, and may accordingly be regarded as the type of the genus. It is easily recognizable by the rather broad, oval body, the distinctly separated eyes, and more especially by the form of the terminal segment of the metasome, and the deep emargination occurring on the inner plate of the uropoda, outside the tip. The name emarginata proposed by Leach, was, indeed, derived from this last character. Occurrence. This species occurs rather frequently along the whole coast of Norway, from the Christiania Fjord to Vadso, being more generally found on the cod, but occasionally also on other kinds of fishes, for instance the haddock, the ling, the halibut and the shark. It is also not infrequently taken up in the dredge, but, as a rule, only young specimens are caught in this manner. Distribution. British Isles (Sp. Bate), Kattegat (Meinert), North Sea (Metzger), Ireland (Edwards), Spitsbergen (Miers), Greenland (Liitken), Atlantic coast of North America (Harger). 60 2. &g& tridens, Leach. (Pi. XXV, fig. 1.) jEga tridins, Leach, Trans. Linn. Soc. Vol. XI, p. 370. Specific Characters. Pody somewhat more elongated than in the preced- ing species, being nearly 2 and a half times as long as it is broad. Cephalon rather broad in proportion to its length, and slightly produced in front. Meso- some moderately convex above, and quite smooth, though having the transverse lines of the 4 posterior segments very distinctly marked. Metasome rather broad, with projecting epimera; terminal segment subtriangular, with the tip bi-sinuate, or projecting in 3 obtuse dentiform projections, dorsal face with 3 obtuse carinse, the median one rather narrow, the other 2 gradually widening in front. Eyes, an- tenna?, and legs nearly as in ^E. psora. Uropoda with the inner plate obliquely truncated at the tip, and devoid of any emargination outside. Length 38 mm. Remarks. This form, established by Leach, is nearly allied to the pre- ceding species, though easily distinguishable by the shape and sculpturing of the terminal segment of the metasome, and by the absence of a sinus outside the inner plate of the uropoda. It is also of a somewhat more oblong form than the said species. Occurrence. Two specimens of this form are preserved in our University Museum, having been taken in the Christiania Fjord from the skin of the com- mon cod. It has also been taken occasionally at Bergen and at Christiansund, but seems, on the whole, to be very rare. I have not myself observed it in a living state. Distribution. British Isles (Leach), Faroe Islands (Schodte & Meinert). 3. vEga Stromii, Ltttken. (PI. XXV, fig. 2.) Stfilnm, Liitken, Vid. Medd. Nat. For. Kjobenhavn 1858, p. 68, PI. I. A, fig.s 68. Syn: ^Eya monophthalma, var., Johnst. bicarinata, Rathke (not Leach). ti}i<'cific Characters. Body oblong oval, more than 2 and a half times as long as it is broad, and rather convex above. Cephalon moderately broad, slightly produced in front. Mesosome with the dorsal face smooth, transverse lines of tlic 4 posterior segments well defined. Terminal segment of metasome narrowly truncated at the tip, with the posterior edge very slightly emarginated, dorsal face with 2 rather slight and obtuse carinse gradually disappearing in front, edges smooth, finely ciliated. Eyes very large, meeting above in the middle, along a 6] straight line. Antennae about as in the 2 preceding species. Anterior pairs of' legs rather strong, with the meral joint slightly sinuated inside, posterior pairs not much elongated. Uropoda as in ^E. tridcns. Colour of a young specimen: light yellow, with scattered reddish specks, posterior part of mesosome dark bluish with opaque white pigmentary ramifications in the middle of the segments. Length of adult animal reaching to 48 mm. Remarks. According to prof. Liitken, the form recorded by Strom in his description of Sondmore, as "Fiskebj0rn", is undoubtedly referable to this species. The same form was subsequently observed off the British Isles by Johnston, but was only regarded as a variety of his ^E. monophthalma. H. Rathke referred the species erroneously to JE. bicarinata Leach, which is a very different species not yet found on the coasts of Norway. Under such circumstances, the name +E. Stromii, proposed by Liitken, ought to be retained for the species. It is easily distinguishable from the 2 preceding species by the very large eyes, which meet along the median line ; and also by the shape of the terminal segment of the metasome. Occurrence. The species would seem to occur not infrequently along the whole south and west coasts of Norway, and extends northwards at least to the Lofoten Islands. It is generally found on the skin of the common cod, but, as is the case with several other species, it seems also to infest several other kinds of fishes. I have myself taken it in the Trondhjem Fjord, from the haddock and from the common picked dog-fish (Acanthias). Distribution. British Isles (Johnston), Skagerak (Schodte & Liitken), Faroe Islands (Liitken). 4. jga erenulata, Liitken. (PL XXV. fig. 3.) JEga erenulata, Liitken. Vid. Medd. Nat, For. 1858, p. 70, PI. 1. A, figs. 4, 5. Specific Characters. Very like the preceding species, but of larger size and coarser structure, the dorsal face being finely scabrous, owing to numerous small, de- pressed pits, and having the transverse lines of the 4 posterior pedigerous segments very distinctly marked. Coxal plates rather large, and less acutely produced poste- riorly. Metasome rather broad, with the epimera of the anterior segments projecting beyond the sides of the mesosome; terminal segment narrowly truncated at the tip, with the posterior edge nearly straight, and distinctly crenulated, upper face plain, without a trace of carinaj. Eyes large, meeting above along the median line. Antennae about as in J5". Stromii. The 3 anterior pairs of legs, on the other hand, distinguished by a very conspicuous cultriform spine, issuing from 62 the end of the propodos, inside the base of the dactylus. Posterior pairs of legs and uropoda nearly as in ^E. Stromii. Length of adult animal reaching to 52 mm. Remarks. The present species, established by Prof. Lutken, is very nearly allied to JE. Stromii, and may easily be confounded with it. On a closer exa- mination, it is, however, found to differ in the much coarser sculpturing of the dorsal skin, and the entire absence of any keels on the terminal segment of the inetasome, the posterior edge of which, moreover, exhibits a pronounced crenula- tion, not found in +E. Stromii. The peculiar cultriform spine issuing from the end -of the propodos of the 3 anterior pairs of legs, affords another character, by which this species is distinguished from all the other Norwegian forms. It is the largest of our indigenous Mgse. Occurrence. Several specimens of this species are preserved in our Uni- versity Museum, having been procured from time to time, partly in the Christiania Fjord, partly off the south coast of Norway. It has, moreover, been observed at Bergen, in the Trondhjem Fjord and in Komag Fjord, West Finmark. In every instance, it has been taken from the skin of the great shark (Scymnus microcephalus). Distribution. Iceland (Lutken), Greenland (Lutken). 5. yga monophthalma, Johnston. (PI. XXVI, fig. 1.) a in<>iH>i>lttli marginal spinules, inner one much broader, widening distally. with the tip blunted and the outer edge slightly emarginate near the end. Colour whitish. Length of an apparently adult specimen 10 mm. Remarks. This form was first recorded by the present author in 1872 as C. Cranchi, Leach. Subsequently, however, I found that it agreed much more closely with the North American species C. concharum Stimpson, and it was re- corded under this name in the Report on the Crustacea from the Norwegian North Atlantic Expedition, as also in my synopsis of Crustacea of Norway. According to Dr. Hansen, who has studied the several species of this genus very carefully, it differs, however, in some particulars also from the North American species, so that it should more properly be regarded as a distinct species, for which the name proposed by Dr. Hoek in 1882 ought to be retained. From C. borealis it may be easily distinguished by its more oblong form, the small size of the eyes, the com- paratively short inferior antennae, the rather different structure of the last pair of legs, and finally by the form of the terminal segment of the metasome and that of the uropoda. Occurrence. Only 2 specimens of this form have hitherto been observed by me, the one being found, many years ago, inside the Storeggen bank, west coasst of Norway, the other being taken during the Norwegian North Atlantic Expedition, east of Vardo. Distribution. The Barents Sea (Hoek). Gen. 2. Eurydlce, Leach, 1815. Syn : Slabberma, v. Beneden. Generic Characters. Body resembling in its external appearance that in the genus Cirolana, though having the metasome comparatively more fully deve- loped, with the penultimate segment of same appearance as the preceding ones, and the terminal segment very large and broad. Eyes well developed, lateral. 73 Superior antennae very small, with the first joint of the peduncle quite short, and extended straight in front, at a right angle to the remaining part of the antenna. Inferior antenme very slender, with the last peduncular joint much elongated. Oral parts on the whole resembling those in Cirolana. Anterior pairs of legs rather short and thick, the 4 posterior ones gradually increasing in length, and having the outer joints broad and compressed. Pleopoda of normal structure. Uropoda with the basal part only very slightly produced inside, rami compara- tively broad, lamellar, and edged with long seta?. Remarks. This genus, established by Leach, is very nearly allied to Cirolana, though differing in some particulars, so as to justify its separation. The genus Slaltberina of v. Beneden is undoubtedly identical with Leach's genus. We know of about 8 species, one of which belongs to the fauna of Norway, and will be described below. Eurydice pulchra, Leach. (Fl. XXX, fig-. 2.) Ewydicc piJchra, Leach. Trans. Linn. Soc. XI, p. 370. Syn : Slabberina again, \. Beneden. ayilis, G. 0. Sars. gracilis, Bovallius. Specific Characters. -Body in adult specimens rather short and stout, oval in form, and rather convex above. Cephalon evenly rounded in front. Coxal plates well defined, and quite smooth. Metasome about the length of the 5 poste- rior segments of mesosome combined, 1st segment very short, almost concealed; terminal segment very large, about the length of the preceding ones combined, and semi-oval in form, tip obtusely rounded, and armed with 4 minute spinules. being, moreover, fringed with small bristles. Eyes rather large, oval triangular, extending a little up the dorsal face. Superior antenme with the flagellum 5-articulate, 1st joint much larger than the other 4 combined. Inferior antenme. when reflexed, reaching almost to the end of the mesosome. last joint of the peduncle about the length of the preceding joints combined, flagellum extremely slender, and composed of about 20 articulations. Legs densely setiferous, and armed with scattered short spines; last pair with the meral and carpal joints much expanded, propodal joint about the length of the carpal one, but considerably narrower; dactylus in all pairs rather small. Uropoda with the basal part densely setous outside, and having a single bristle at the inner corner, terminal plates rather unequal, the inner one being much broader than the outer, and obliquely truncated at the end. Body ornamented dorsally with richly ramified, dark, pig- 10 Crustacea. 74 mentary stars, arranged in transversal rows on the segments, and partly con- fluent. Length of adult animal 7 mm. Remarks. As pointed out by v. Beneden, this form was recorded by Slabber as early as in the year 1778. under the Dutch name "Agaat-Pissebet", and the specific name ayata applied to this form by v. Beneden should therefore per- haps be preferred to that proposed by Leach (puUhra)] but the Leachian name has been so generallyd used, that it would be inappropriate to change it, The form recorded by the present author as Slabberina ay His, is undoubtedly the same species, and I also fully agree with Dr. Hans en in regarding the Slabberina yra- cUis of Bovallius as only founded on a young specimen of the present species. Occurrence. I have observed this form rather plentifully in the inner part of the Trondhjem Fjord, at Levanger, where it occurred close to the shore in quite shallow water, swimming rapidly about between the stones in a manner very similar to that -observed in the Dytisci and Gyrini. I have also taken it near the sandy beach of Listerland. and occasionally in the Christiania Fjord, at Laurkullen and Fredriksvsern. According to Dr. Bovallius. the specimen de- scribed by him as Slabberina yracilis, was taken up in the dredge at Drobak from a depth of 100 fathoms; but it is most probable, as opined by Dr. Hansen. that it did not come from this depth, but had entered the dredge during its uphauling. Distribution. British Isles (Leach). Kattegat (Meinert), Baltic at Kiel (Moebius), Dutch coast (v. Beneden). coast of France (Bonnier). Fam. 5. Limnoriidae. Characters. Body subdepressed, capable of being rolled into a ball. Ce- phalon short and very convex. Coxal plates behind the 1st segment of mesosome well denned, laminar. Metasome composed of G well-defined segments, the last of which is very large, clypeiform. Antenna? small, subequal in size. Oral parts on the whole normal, adapted for biting. Legs of uniform structure, all being am- bulatory in character. Pleopoda well developed, serving both for swimming and breathing; 1st pair of same structure as the succeeding ones; 2nd pair in male with a lateral stylet on the inner plate. Uropoda comparatively small, lateral, rami not lamelliforni. Ib'innrk*. This family, first established by 0. Harger. is not difficult to distinguish from any of the preceding ones, whereas in certain points it 75 exhibits an unmistakable likeness to the family Sphceromidce, not represented in the fauna of Norway, and I had, indeed, formerly combined the two. There are, however, some distinguishing characters which make it advisable to keep the two families apart. On the other hand, I find it quite inadmissible to associate this family with the Asellota, as proposed by some authors. The full segmentation of the metasome, the uniform structure of the pleopoda, and the lateral position of the uropoda, prove it unquestionably to belong to the group Flabellifera, as here de- fined. The family comprises as yet but a single genus. Gen. Llmnoria, Leach, 1815. Generic Characters. Body oblong, rather convex above, with the segments sharply marked off from each other. Cephalon comparatively short and blunt in front, with the buccal mass very prominent below. First segment of mesosome longer than the other, and partly advancing over the cephalon. Coxal plates on the succeeding segments, rather large, deflexed, the posterior ones triangularly produced. The 5 anterior segments of metasome with well-developed, laterally projecting epimera; terminal segment broad, flattened above. Eyes wide apart, lateral. Antennae with the flagella rather short. Mandibles very strong, cutting edge terminating in a conically compressed, chisel-shaped point, molar expansion wanting, palp rather small. Anterior maxillae with the masticatory lobe conically tapering and coarsely spinous at the tip, basal lobe narrow, turned anteriorly, and carrying 3 short, ciliated apical setse. Posterior maxillse terminating in 3 setiferous lobes, the innermost representing the masticatory lobe. Maxillipeds slender, with the basal part rather elongated and narrow, masticatory lobe well developed, palp composed of 5 flattened joints, epignath lanceolate, turned ante- riorly. Anterior pairs of legs somewhat shorter than the posterior, dactylus in all pairs provided inside with a secondary claw-like projection. Pleopoda with the rami lamellar, and, excepting the last pair, densely fringed with setse. Uro- poda with the outer rainus short, ungtiiform; inner, linear. Remarks. This genus was established by Leach in the year 1815, to in- clude the peculiar little creature, whose destruction of pile-work and other sub- merged timber had long been known. He associated the genus with the Cymothoidce and Sphwomidc?, thus recognizing its true relationship. We know, as yet, of only 3 species, one of which, L. seqnis Chilton, has been found off New Zealand, the 2nd, L. antarctica Pfeffer, at the South Georgian Islands, the 3rd being widely distributed in the northern Ocean. 76 Limnoria lignorum (Eathke). (PI. XXXI.) Cymothoa lignorum, Ratlike, Skrifter af Naturh. Selsk. Vol. 101, PI. 3, fig. 14. Syn: Limnoria tcrebrans, Leach. untinata, Heller. Specific Characters. Body, when fully extended, about 3 times as long as it is broad, and almost semi-cylindric in form, slightly tapering in front. Cephalon nearly globular, and partly covered above by the 1st segment of mesosonie, front obtusely rounded. First segment of mesosome considerably longer than the others and rather deep, forming below, on each side, a rounded lobe projecting over the lateral faces of the cephalon. Coxal plates fringed with ciliated bristles, the 2 {in- terior pairs oval quadrangular, the 4 posterior ones considerably larger, and pro- duced to an acute corner pointing backwards. Metasome considerably exceeding half the length of the mesosome, and scarcely narrower, epimera triangular, projecting laterally; terminal segment about the length of the other 5 combined, and very broad, almost elliptical in form, posterior edge evenly arcuate and finely ciliated. Eyes comparatively small, rounded, with a limited number of large cornea;. Supe- rior antennee somewhat stronger than the inferior, with the flagellum extremely small, 3 -articulate, and carrying a dense fascicle of long sensory filaments. Inferior antenna 1 with the flagellum about half the length of the peduncle, and composed of 5 articulations, the 1st of which is much the largest. First pair of legs somewhat larger than the next succeeding ones, but otherwise of the very same structure, meral and carpal joints in most of the legs strongly tubercular inside. Last pair considerably more slender than the others, and without any tubercles. Dactylus in all legs distinctly bi-articulate, the 1st joint having at the end inside, a bidentate unguiform spine. Uropoda with the .basal part strongly tuberculated outside, and projecting between the rami to an acute projection, outer ramus short, unguiform, turned outwards, inner sublinear, about the length of the basal part, and terminating in a dense bunch of slender bristles. Colour light greyish brown, with darker brown pigmentary ramifications. Length of adult animal 5 mm. Remarks. This form was described by Kathke as early as in the year 1799 as Cymothoa lignorum. By subsequent authors, it has generally been re- corded under the name given to it by Leach, viz., Limnoria terebrans. The Lim- noria imcinata of Heller, from the Adriatic, is undoubtedly identical with the northern species. Occurrence. I have found this form not infrequently in the Christiania Fjord, at Drobak and Moss, boring in immerged pieces of wood. A single 77 specimen was, moreover, taken by me many years ago at the Lofoten Islands. It thus appears that it occurs along the whole south and west coasts of Norway. Distribution. British Isles (Leach), Kattegat (Meinert), Dutch coast (Hock'. coast of France (Bonnier), Adriatic (Heller), Black Sea (Sowinsky), atlantic co;ist of North America (Harger). Tribe 3. VALVIFERA. Remarks. The chief character by which this group is defined from all other known Isopoda, consists in the peculiar structure of the uropoda, which, like a pair of folding doors, arch over the lower face of the metasome, thus form- ing a shelter for the delicate pleopoda, the latter being for the most part branchial in character, though the anterior pairs may at times also serve as swimming limbs for propelling the animal through the water. We only know of 3 families belong- ing to this tribe, viz., the Idotheidce, Arctitridce and Cludiludw, the last of which, however, is still very imperfectly known. The first 2 families are represented in the fauna of Norway, and will be treated of below. Fam. 1. Idotheidae. Characters. Body more or less depressed, with the segments of mesosome of uniform appearance, coxal plates sometimes distinctly defined, sometimes confluent with the segments. Metasome with some, or all of the segments consolidated to form a large terminal piece, carrying the normal number of pleopoda. Superior jintennse comparatively small, with the flagellum mii-articulate. Inferior antennae more or less elongated, and originating outside the superior, from the lateral corners of the cephalon. Oral parts on the whole normal, though the mandibles are al- ways without palps,^and the joints of the maxillipeds are often reduced in number. Legs rather strongly built, increasing in length posteriorly, the 3 anterior pairs 79 being sometimes pronouncedly subcheliform in structure. The anterior pairs of pleopoda with the rami densely setiferous, 2nd pair in male with the usual stylet. Uropoda very large, lamellar, valve-like, closing over the lower face of the meta- some; outer part cut off by a transverse suture, and forming a separate plate, in- side which sometimes occurs another much smaller plate. Incubatory pouch normal. Remarks. This family is chiefly distinguished from the Arcturida> by the more or less broad, depressed body, the rather uniform segmentation of the mcso- some, and the structure of the legs. Some of the largest known Isopoda are in- cluded in this family. Thus the huge Gtyptonotus antarcticus measures no less than 3 inches and a half in length, and some of the arctic species of the genus Chiridothea are scarcely smaller. The family comprises about 10 genera, only one of which is represented in the fauna of Norway. Gen. IdOthea, Fabr., 1798. Generic Characters. Body oval or oblong, distinctly depressed, with the coxal plates, beyond the 1 st segment of mesosome, well defined, laminar. Cephalon subquadrate, with the lateral parts not expanded. Metasome with 3 short seg- ments exposed in front of the terminal one, the 3rd segment being, however, less perfectly defined dorsally. Eyes distinct, lateral. Superior antenme with the flagellum short, clavate; inferior antenme with the flagellum more or less elongated and multiarticulate. Mandibles very strong, with the cutting edge divided into 2 superposed dentated lamellae, molar expansion large and thick. Both pairs of maxilla? of quite normal structure. Maxillipeds with the palp 4-articulate, last joint lamellarly expanded, masticatory lobe well developed, epignath oblong oval, turned in front. Legs of rather uniform structure, ambulatory, and as a rule more strongly built in male than in female, sometimes approaching to a subcheli- forni character, dactylus in all pairs strong, unguiform, unequally bidentate at the tip. Uropoda terminating in a single flattened joint, and having at the base of this joint, outside, a strong ciliated seta. Male, as a rule, much larger than female. Remarks. This is the genus first established, and it accordingly may be regarded as the type of the family. Numerous species have been described by different authors from different parts of the Oceans, bat some of these ought certainly to be separated generic-ally, and even in the restriction adopted by Mr. 80 E. Miers 1 ), the genus comprises, in my opinion, forms which can hardly be placed in one and the same genus. As to the Norwegian Idothere, they have generally been considered by recent authors as only varieties of one and the same species. A close]- examination of i'he large material at my disposal has. however, shown them in reality to be referable to no less than 6 different species, all easily re- cognizable in both sexes. i 1. Idothea baltiea (Pallas). (PI. XXXII.) Oitiscns bfiltirus, Pallas, Spir. Zool. Vol. IX. p. 6fi. PL IV, tig. 6. Syn: Stenosoma irrorata, Say. Jilntlica tricnspvlata, I)esm. tritlenlata, Rathki'. irrorata, Harger. marina, Miers. Specific Characters. Body oblong oval, about 3 times as long as it is broad, with the dorsal face perfectly smooth. Coxal plates rather large, occupying the whole length of the side-edges of the segments, so as to form a broad, conti- nuous marginal area. Metasome about the length of the 5 posterior segments combined, terminal segment slightly tapering distally, side-edges straight, tip dis- tinctly tridentate, middle tooth conically produced, lateral ones much shorter, though well denned, and each separated from the median tooth by a well-marked sinus. Eyes of moderate size, rounded. Superior antenna? with the 1st joint of the peduncle rather broad, irregularly angular, last joint much longer than the middle one, flagellum about the length of the former. Inferior antennae rather elongated, reaching, when reflexed, almost to the end of the 3rd segment of meso- some, flagellum very slender, being much longer than the peduncle, and composed of from 16 to 20 articulations. Legs moderately strong, being, as usual, more powerfully developed in male than in female. Stylet of the 2nd pair of pleopoda in male not extending to the end of the inner plate. Uropoda with the terminal plate obtusely truncated at the tip. Colour extremely variable, sometimes uni- formly yellowish or greenish with small dark dots, sometimes variegated, with dark brown pigment forming regular longitudinal bands or larger patches arranged in a perfectly symmetrical manner. Length of adult male reaching to 35 mm. Remarks. Mr. E. Miers names this form Llotliea marina, believing that Linnaeus' Oniwns mar'nitt* refers to this species. This is. however, very doubtful, and as that specific name has been more properly applied to another Tsopod, ') Revision of the Uluteid^. Linn. Sue. Journal. Zoology. Vol. XVI. Ta n a i d ae. I s op o da. PI. 17 G.O. S ars, autogr. I. Pseudotanais forcipatus,(Lilljeb.) Liiljeborgii, G.O. Sars Ta na i d SB. I s opo da. PI. 18. G.O. S ars, autogr. Pseudoianais macrocheles, G.O.Sars. Anthuridas. Is op PI. 19. -\ /? ^ -/*--: /'> *--'> G.O. S ars, autogr. I.Calathura norvegice, G.O.Sars. 2. i, brachiata. (Stimps). Anthuridae. I s opo da.. PI.20. G.O. S ars, autogr . Leptanthura ienuis, G .0. Sars. Gnaihiidas. I s opo PI. 21. G.O. S ars, autogr . Gnaihia maxillaris, (M-Edwj. Gnathiidae. I s op o da.. PI. 22. 53! ' ' I.-.,- > ...; . yr^fs I- , -,.^i - i ^- - ^ ?' i v ;>WS3r s '' - ^ --v .* -. L* - ^ ' - ^ 1 , - G. 0. S BTS, autogr . I.Gnaihia maxillaris (coniin.) 2. deniaia, G.O. Sars. Gnathiidas. I s op o PI. 23 ;--- -' g '" ^ -! ,. -'. L -k?F --- ' I- V \/^ ,vS 3 -' ' * !< * <: *? : i^*.J ^ - ;f (>"' G.O. S ars, autogr . 1. Gnathia elongata, (Kroyer). 2. abyssorum, G. O.Sars, /tgidae. I s opo da- i. 24. OL, G.O.Sars. autogr. psora , ( Linne). Aigidae. I s op o da__ PI.25. . i ; ; ;/ k -'. ', v^ky ^w / . - . ..'''' '.-'.- - ::;/^ S-: . :- - '-?' ^ y - - G.O. S ars, autogr. 1. /tga irfdens, Leach. 2. Stromii, Luiken. 3. crenulaia, LiJtken. fegidae. Is opo da.. PI. 26. ....,-... . '! v ^ G. 0. S ars, autogr . 1. /tgs monophihslma, Johnst. 2. arctica, Lulken. 3. ventrosa, M.Sars. I s opo da. PI. 27. - ~r^ G. 0. S ars, autogr . Rocinela danmoniensis , Leach, I s opo da. PI. 28. G.O. S ars, autogr . Sj/scenus infeh'x, Harger (jun GiroSanidse. I s opo da. Pi. 29, G.O. S srs, autogr . Cirolana borealis, Lilljeb. Cirolanid I s opo da. PI. 30. .,-.,..- (1 * -' "^ m- r G.O.S ars, autogr. !. Cirolana microphthalma, Hock 2. Eurydice puichra, Leach. Limnoriidse Is opo PI. 31. G. 0. S ars, autogr . Limnoria lignorum, Rathke . Idotheidas. I s opo da. PI.32. \ ': ' - , ' m i - v fc fc&'- I ^ iY ^.fr^riF" ^ & i t -^--.7^ -^_" - * * 71 . '. ',.' 1 G.O. S ars, autogr . jdothea balthica, (Pallas), 81 viz., laem marina, it is best to adopt the name baltica proposed by Pallas, which name undoubtedly refers to the present species. The name under which this form lias more generally been recorded, is that of Idothca tricuspidata Des- merest; but the Pallas' name ought certainly to be preferred as the much older one. It is the largest of the Norwegian Idothese, and easily recognizable in both sexes by the form of the terminal segment of the metasome, which I have found to be pretty constant even in very young specimens. As is the case with other species of the genus, the form of the body in fully grown, ovigerous females slightly differs from that in male specimens, in so far as the greatest width occurs somewhat farther forward, or across the middle of the incubatory pouch. The male is also considerably larger than the female, and has the coxal plates c< imparatively broader. Occurrence. The species occurs rather frequently along the whole Nor- wegian coast, from the Christiania Fjord at least to Tromso, in comparatively shallow water among algpe. Though being more generally of a rather stationary habit, slowly creeping about on the bottom, the animal is by no means devoid of swimming power. At times it may even be seen to move rather rapidly through the water. In doing so, the valvular uropoda are found to be widely separated, so as to allow the free play of the anterior pairs of pleopoda, by the strokes of which, the animal is propelled through the water. Distribution. British Isles (Sp. Bate), Kattegat (Meinert), Baltic (Pallas), Dutch coast (Hoek), coast of France (Bonnier), Mediterranean (Heller), Black Sea (Czerniawsky), Atlantic coast of North America (Harger). 2. Idothea pelagica, Leach. (PI. xxxur.) Idotltea -pday'ica, Leach, Trans. Linn. Soc. Vul. XI, p. 3B"i. Syn: Idothca brcricorms, Eatliko. torosa, Eaihke. Specific Characters. Body comparatively short and stout, being scarcely 3 times as long as it is broad, with the segments very sharply marked off from each other. Coxal plates in both sexes comparatively small, not contiguous. Me- tasome scarcely more than half the length of the mesosome, terminal segment rather broad, and rounded at the tip, with only a very slight indication of a median prominence. Eyes comparatively large, rounded. Superior antennae with the last joint of the peduncle but little longer than the 2nd. Inferior antenna 1 unusually short and robust, scarcely reaching beyond the 1st segment of mesosome 11 Crustacea. 82 flagellum much shorter than the peduncle, and rather thick, being composed, in female, of 7, in male, of 9 articulations only. Legs in both sexes very strongly built, those in male having, inside the outer joints, a dense fringe of delicate cilia. Second pair of pleopoda in male with the stylet reaching beyond the inner plate. Uropoda rather broad, with the terminal plate blunted at the tip. Colour some- what variable, more or less dark brownish, with irregular shadows of a darker hue. Length of adult female 9 mm., of male 13 mm. Rfmarl*. There cannot be any doubt that this is the true 7. pclagica of Leach-, and that the form at first described by H. Rathke as I. Iret'icornis and subsequently named by him /. torosn, is the very same species. By recent authors this form has generally been regarded as only a variety of I. laltica; but I believe that in doing so, they cannot have examined the true Leachian species, which it is impossible to confound with 7. Imlticn. As will appear from the figures here given, this form is in fact a very distinct and easily recognizable species, well distinguished in both sexes by its short and stout body, the small coxal plates, the short and robust inferior antennae, and the unusually strongly built legs. Moreover, the terminal segment of the metasome exhibits a form rather different from that in the other Norwegian species. Occurrence. Rathke found this form at Christiansund nmong Hfytihix growing close to the shore. I have myself taken it in another locality, viz. out- side Lillesand. south coast of Norway, where it occurred likewise close to tin- shore, among alga?. Distribution. British Isles (Leach. Sp. Bate), coast of France (Bonnier). 3. Idothea granulosa, Rathke. (I'l. XXXIV, fig. 1.) Idotlica (jramdosa, Rathke. Beit rage zur Fauna Norwegens, p. 23. Specific (harnct< > r$. Body oblong oval, somewhat more than 3 times as long as it is broad, with the dorsal face distinctly, granular being covered with small de- pressed pits. Coxal plates comparatively small, not contiguous. Metasome in male comparatively longer than in female, equalling in length the li posterior segments of mesosome combined, terminal segment in both sexes considerably attenuated, lan- ceolate, terminating in a rather prominent conical projection, lateral corners rounded off. Kves of moderate si/e. Superior antenna 1 with the last joint of the peduncle about the length of the 2nd. Inferior antenna- a little longer than in 7. jtcliujica. though scarcely reaching to the end of the 2nd segment of mesosome, flagellum not attaining the length of the peduncle, comparatively narrower than in the said 83 species, and composed of from 8 to 10 articulations. Legs moderately strong. Stylet of 2nd pair of pleopoda in male reaching somewhat beyond the inner plate. Uropoda with the terminal plate obliquely roiyided at the tip. Colour uniformly light reddish blown. Length of adult female 11 mm., of male 15 mm. jRewto'l'*. This form briefly described, but not figured, by Rathke under the above name, has generally been regarded as only a variety of 1. lialiica. It is certainly, however, a well-defined species, differing, as it does, from the type species not only in the far inferior size, but also in several anatomical details mentioned in the above diagnosis. It is best recognized by the narrow, lanceolate form of the terminal segment of the metasome, which is perfectly con- stant in all specimens. Occurrence. Rathke found this form at Christiansund and Trondhjem. I have myself occasionally met with it on the sandy beach of Listerland, and in the outer part of the Christiania Fjord, where it occurred in quite shallow water. Out of Norway it has not yet been recorded. 4 Idothea viridis (Slabber), (PI. XXXIV. fig. 2.) Oniscus viridis, Slabber, Naturk. verlustigingen, p. 104, PL XII, figs 4 5. Syn: Idotca pliosplwrea, Hoek (not Harger). Specific Characters. Body very slender, oblong linear in form, more than 4 times as long us it is broad; that of male, as usual, still more slender than in the female. Cephalon but little broader than it is long, frontal margin slightly concaved. Coxal plates comparatively small, not contiguous. Metasome occupying about V 3 of the length of the body, last segment but very slightly narrowed distally. and terminating in a comparatively short and obtuse median prominence, lateral cor- ners distinct, though obtuse. Eyes of moderate size. Superior antenna 1 nearly as in /. granulosa ; inferior antenna^, on the other hand, comparatively more slender, reaching beyond the 2nd segment of mesosome, flagellum exceeding the peduncle in length, and composed of from 10 to 15 articulations. Legs more slender than in most other species, though, as usual, somewhat stronger in male than in female. Stylet of 2nd pair of pleopoda in male extending considerably beyond the inner plate. Uropoda with the terminal piece obtusely truncated at the tip. Colour uniformly greenish. Length of adult female lo mm., of male 12 mm. lu'warf.*. The 2 detail-figures (PI. VII, figs 2, 2 r) given by Dr. Hoek in the 2nd part of his "Crustacea Neerlandica' 1 ') leave no doubt that the form l ) Tijdsdir. Nederl, Dierk. Vereyniging. 2 series, Vol. 2, P;sr( .'!, 84 he records as I. phosphor ca Harger is the very same species as that here treated of. It can scarcely be identical with the North American species, whereas it is most likely that Dr. Hook is right in considering the nincus riridis of Slabber to be the same species. In any case, the specific name proposed by Slabber ought to be retained as the much older one. Before becoming acquainted with Dr. Hoek's paper I had named this form 7. angusta, owing to its unusually narrow form of body, and it is so named in the plate. From the other Norwegian Idothea? it is at once recognized by its slender form, which approaches to that in the genus Stenosoma. The manner in which the last segment of the metasome terminates, somewhat resembles that in 7. baltica, there being traces of a tridentate shape; but the median prominence is considerably shorter and blunter, and the lateral corners very obtuse. Occurrence. I have taken this form rather plentifully in the Christiania Fjord, at Moss, in quite shallow water among eel-grass. Distribution. Dutch coast (Hoek), coast of France (Hoek). 5. Idothea neglecta, G. 0. Sars, n. sp. (PI. XXXV, fig. 1.) Specific Characters. Body oblong oval in form, scarcely 3 times as long ;is it is broad, and. as usual, comparatively shorter and stouter in female than in male, with the greatest width farther forward. Cephalon about twice as broad ;is it is long, frontal margin straight. Coxal plates in female not very large, and scarcely contiguous, in male much more fully developed, and forming together on each side, as in 7. bnHica, a broad marginal area. Metasome exceeding y 3 of the length of the body, last segment but slightly narrowed distally, and termina- ting in a blunt point, lateral corners obsolete. Eyes rather large. Superior an- tenna 1 with the last joint of the peduncle longer than the 2nd. Inferior antennna 1 rather slender, reaching to the end of the 2nd segment of mesosome, flagelluin much longer than the peduncle, and composed ".f from 16 to 20 articulations. Legs moderately strong. Stylet of 2nd pair of pleopoda in male very short, not n 'aching far beyond the middle of the inner plate. Uropoda with the terminal piece transversely truncated. Colour generally very dark brown or almost black, sometimes lighter, variegated with small, irregular patches. Length of adult female 16 mm., of male 25 mm. Hematics. There cannot be any doubt that this very common form must have been observed by several authors. It has, however, not yet been recognized as a distinct species, but has either been regarded as merely a variety of 7. baltica. 85 or as I. pelayica of Leach. The latter mistake has hecn previously committed by the present author; but after having become acquainted with the true /. pelagica Leach. I now find that it is a very different species, exhibiting a much closer relationship to I. emarginata,. From this species, however, it is at once distin- guished by the very different form of the last segment of the metasome. in which respect it also differs conspicuously from the North American /. phosphor ea. Occurrence. The species occurs along the whole Norwegian coast, from the Christiania Fjord to Vadsd. and is often found in great abundance among decaying alga?, in depths ranging from 6 to 20 fathoms. As to its distribution out of Norway, it is impossible at present to state anything with certainty; but it is most likely that it also occurs at any rate off the British Isles and in the Kattegat. 6. Idothea emarginata (Fain-.). (PI. XXXV, fig. 2.) Cymothoa emarginata, Fabricius. Entom. Syst. II, p. 508. Syn: IdotJica extisa, Bosq. oestrum, Pennant. Specific Characters. Body oblong oval, scarcely 3 times as long as it is broad, and much larger in male than in female. Coxa! plates in female rather small and not contiguous, in male much larger, and forming on each side a broad marginal area. Last segment of metasome abruptly truncated at the tip, hind edge slightly emarginated, with the lateral corners distinctly projecting. Eyes and superior antennae about as in I. neylecta. Inferior antenna; somewhat less slender, scarcely reaching to the end of the 2nd segment of mesosome, flagellum not much longer than the peduncle, and composed of from 12 to 1(5 articulations. Legs about as in /. neglccta. Stylet of 2nd pair of pleopoda in male somewhat longer than in /. neglccta, though not reaching to the end of the inner plate. Uropoda with the terminal piece slightly emarginated at the tip. Colour rather variable, sometimes uniformly dark brown, sometimes variegated with larger whitish patches, which are often confluent along the sides, so as to leave the marginal area?, formed by the coxal plates, uncoloured. Length of adult female 18 mm., of male 30 mm. Remarks. This species was recorded as early as in the year 1793 by Fabricius, as Cymothoa emarginata. By earlier British authors (Pennant and Leach) it was named Idothea oestrum. Though very nearly allied to I. neglecta, this form is readily distinguished, both from that species and the other Norwegian Idothese, by the abruptly truncated and emarginated terminal segment of the meta- some, for which reason it has never been confounded with any of the other species. 86 Occurrence. The species has a distribution along the Norwegian coast similar to that of 1. ncglecta, and is generally found in company with that species. It is. however, on the whole, less frequent, though in one locality, at Farder, in the outermost part of the Ghristiania Fjord, I found it in considerable abundance among decaying algse, in a depth of about 20 fathoms. Distribution. British Isles (Sp. Bate), Kattegat (Meinert). Fam. 2. Arcturidae. Characters. Body narrow, scarcely at all depressed, approaching to a cylindric form. Coxal plates small, though distinct. Metasome with the segments more or less consolidated, the last one rather large. Superior antenna} small, with the flagellum uniarticulate. Inferior antenna? very strongly developed, pedi- form, the outer joints of the peduncle being much elongated and connected by geniculated bends, flagellum comparatively short. Oral parts on the whole re- sembling those in the Idotheidce. The 4 anterior pairs of legs very unlike the 3 posterior ones, and not ambulatory, nor strictly prehensile; the 1st pair very small and closely applied to the oral parts, so as to exhibit more the appearance of maxillipeds; the 3 succeeding pairs of very feeble structure, and fringed with long delicate seta 1 . The 3 posterior pairs of legs normally developed, and rather strongly built, diminishing somewhat in length posteriorly. Pleopoda present in the normal number, the 2 anterior pairs being natatory, with narrow and densely setifcrons plates, the 3 posterior pairs exclusively branchial; 2nd pair in male with a long bi-setose stylet appended to the inner plate. Uropoda, as in the Ido- theidce, valve-like, arching over the lower face of the metasome, and having a small secondary plate inside the terminal one. Male much smaller than female. Remarks. In external appearance, the forms belonging to this family are very unlike those of the preceding one, and were, indeed, by some of the earlier authors, widely separated from them, and associated with a very different family, vi/., the Anthuridas. On a closer examination, however, they are, in fact, found to show nothing in common with the latter family, except the narrow, cylindric form of the body, Avhereas they exhibit a close relationship to the Llothc'idw, both as regards the structure of the oral parts, and that of the metasome. The chief difference consists in the strong development of the inferior antenna 1 , and in the 87 peculiar structure of the 4 anterior pairs of legs. The family comprises as yet 3 genera, viz., Arcturus, Astacilla and Arctnrclla, the last 2 of which are repre- sented in the fauna of Norway, and will he treated of helow. Gen. 1. AStacilla, Cordiner, 1795. Syn : Lcacid, Johnston. Generic Characters. Body extremely slender, suhcyliudric in form, with the middle segment of mesosome very much elongated, heing in male narrow cy- lindric, in female somewhat thicker, and carrying heneath it the incubatory pouch. The 3 posterior segments of mesosome short and very movably articulated, so as to allow the anterior part of the body to be bent dorsally at right angles to the posterior. Metasome with only a single segment distinctly separated in front of the terminal one, which is conically produced behind, and exhibits at the base on each side a small projecting lappet, really indicating the presence of an- other imperfectly defined segment. Eyes large and prominent, lateral. Superior antenna; with the tlagellum more fully developed in male than in female, and in both sexes carrying a number of delicate olfactory filaments arranged along the outer edge. Inferior antenme very much elongated, though having the flagellum extremely short, and only composed of 3 articulations finely denticulated inside, the last terminating in a small spine. Maxillipeds with the palp well developed. 5-articulate, epignath comparatively small, basal part in female produced in a thin ciliated plate extending posteriorly. 1st pair of legs densely setous, proximal part of dactylar joint lamellarly expanded; the 3 succeeding pairs very slender, and fringed with a double row of long seta?, dactylus obsolete. The 3 posterior pairs of legs smooth, dactylus strong, bidentate at the tip. Uropnda with the ter- minal piece triangularly pointed, secondary lamella very small, setous at the tip. Incubatory pouch only formed by a single pair af elliptical valvular lamella- issuing from the middle segment of mesosome. Remarks. As stated by the Rev. Mr. Stebbing, the generic name Asta- cilla, which has generally been attributed to Fleming, was in fact proposed at a much earlier date (1795) by the Rev. Charles Cordiner to designate a species of the present genus. The name Leacla proposed by Johnston in 1825, and used by some subsequent authors, was merely abandoned, because a very similar name, that of. Leachia, had been previously applied to a genus of Cephalopods. In any case, the name Astacilla should be given the precedence, as it is still older than the name 88 Arc-torn* given by Latreille to another genus which has generally been regarded as the type of the family. The name of the family should therefore perhaps more properly be changed to Astaclllidce. The present genus is chiefly distin- guished from Arcturus by the greath. length of the middle segment of the meso- some, which gives the body an extremely slender, nearly cylindrical form, whereas in Arctnrus it is more fusiform in shape. Moreover the structure of the 1st pair of legs is slightly different, and the incubatory pouch, which in Ardunts is formed by 3 pairs of distinct lamella? issuing from the 2nd, 3rd and 4th segments, is here only confined to the middle segment of the mesosome. The genus comprises several species, amounting to about 10 in all. To the fauna of Norway belong 4 species, to be described below. 1. Astacilla longicornis (Sowb.) (PI. XXXVI.) Omscus lonijiciHiils, SdAverliy, Brit. Miscell. T. 19. Syn : Lcacia lacertnsa. Jolmst. ,. Arcturus longicorms, Westw. ., gracilis, G<><>. 163. Specific Characters. Body of female comparatively less slender than in the '2 preceding species, and but slightly tubercular. Middle segment of mesosome not nearly twice as long ;is the preceding part of the body, and exhibiting, quite in front, 2 juxtaposed dorsal tubercles of somewhat larger size than the others. Eyes comparatively smaller than in the 2 preceding species. Superior antenna 1 with the riagellum twice as long as the 2 preceding joints combined, and carrying only 5 olfactory iilamcnts. Inferior antenna 1 with the tlagellum not attaining l /$ 91 of the length of the hist peduncular joint, its 1st joint not twice ;is long as the other 2 combined. 1st pair of legs with the. proximal part of the dactylus com- / paratively longer and more expanded than in A, longicornis. Male resembling that of the latter species, though somewhat less slender. Colour uniformly grey- ish, scmipellucid, without any patches. Length of adult female 13 mm. Remarlcs. This form is also very nearly allied to the type species, and may. at first sight, easily be confounded with it. It is, however, of far inferior size and of somewhat less slender form. On a closer comparison, moreover, some differences in the structure of the several appendages may be found to exist, showing it to be evidently specifically distinct. The uniform greyish colour is another character by which this form may be easily distinguished from ^1. loiuj'i- cornis, which always exhibits a, more or less variegated colouring. Occurrence. I first discovered this form off the Lofoten Islands, in the con- siderable depth of 25o to 300 fathoms. Subsequently I have found it rather abundantly in the inner part of the Trondhjem Fjord, in depths ranging from 100 to 200 fathoms, sometimes clinging to deep-water Hydroids and Gorgonids, sometimes to the spines of Echinus detjaus Dill). & Koren. Out of Norway it has not yet been recorded. 4. Astacilla pusilla, G. 0. Sars. (Pi. XXXVII, fig. 3.) An-lui us ptisiUits, G. 0. Sars. Uidrag til Kuinlskaben om Dyrelivet pa;i vore H;ivl>anker. Cliv. Vicl. Selsk. Foi-h. 1872. p. 93. XjH'cifie Characters. Body of female less slender than in the type species, and very tubercular, some of the tubercles assuming a spiniform character. Cephalon with 2 very conspicuous juxtaposed pyramidal prominences above in the middle. Each of the 3 succeeding segments with a transverse row of 4 tubercles, the 2 uppermost being rather prominent. Middle segment of mesosome coarsely tubercular both dorsally and laterally, the tubercles being subequal in size. The 3 posterior segments of mesosome, as also the metasome, likewise distinctly tu- bercular dorsally. Superior antenna.' about as in A. a f finis. Inferior antennae with the riagellum very small, its 1st joint not being longer than the other 2 combined. Colour uniformly light yellow. Length of adult female scarcely ex- ceeding 8 mm. Remarks. In the general form of the body, this species somewhat re- sembles A. af finis. It is. however, of rather inferior si/e, and much more tuber- cular. The colour also is different. 92 Occurrence. It would seem to be a very rare species. The first specimen was found by the present author on the Storeggen bank, clinging to a spine of Echinus rarispinus G. 0. Sars, taken up from a depth of 80 to 100 fathoms. Another specimen was taken off the Lofoten Islands in about the same depth. Distribution. Skagerak (Meinert). den. 2. ArCtUrella, G. O. Sars, n. Generic Characters. Body less elongated than in Astacilla, and in female, slightly depressed, the middle segment being very large and broad, scutiform. Metasome about as in Astacilla. Superior antennae with only a very restricted number of olfactory filaments issuing from the tip of the flagellum. Inferior an- tennae of no considerable length, flagellum 3-articulate and terminating in a long spine. Maxillipeds with the palp rather slender, 5-articulate, epignath very large and ciliated at the tip. 1st pair of legs with the proximal part of the dactylus narrow^, linear; the 3 succeeding pairs less elongated than in Astacilla, and less richly supplied with seta:. Incubatory pouch confined to the middle seg- ment of mesosome. Male much smaller than female, and having the middle seg- ment of mesosome simple, cylindric in form. Remarks. This new genus is founded upon the peculiar form described by the present author as Astacilla dilatata. A closer examination of this form has shown it also to differ from the species of the genus Astacill't in some ana- tomical details mentioned in the above diagnosis, so that it should more properly be regarded as the type of a distinct, though nearly-allied genus. Arcturella dilatata, G. 0. Sars. (PL XXXVIII.) Astacilla dilatata, G. 0. Sars, Oversigt af Norges Crustaceer I, p. 63, PI. 2, fig. 3. Specific Characters. Body of female very tubercular, some of the tu- bercles assuming a spiniforin character. Cephalon with 2 dorsal juxtaposed, and somew r hat procurved pyramidal prominences, in front of which occur several smaller tubercles. Each of the 3 succeeding segments with a transverse series of 5 co- nical tubercles, the median one being the most prominent, lateral parts triangu- larly produced, those of 1st segment larger and deeper than those of the 2 other segments. Middle segment of mesosome exceedingly large and broad, somewhat 93 longer than the preceding part of the body, and almost quadrate in form, with the anterior and posterior corners laminarly expanded, and connected by a lateral. creimlated crest; dorsal face armed in the middle with 2 very strong juxtaposed spines, slightly curved in front, and having behind them scattered tubercles, hind edge raised, and armed with 3 strong tubercles. The 3 posterior segments of mesosome carinated dorsally, and having laterally scattered tubercles. Metasome with the proximal segment distinctly carinated dorsally and constricted in the middle; terminal segment only carinated in its anterior part, and tapering to an acute point. Eyes rather large and convex, rounded. Superior antennse with the nagellum longer than the 2 preceding joints combined, and carrying, in female 2, in male 3 apical olfactory filaments. Inferior antennse scarcely more than half as long as the body, Hagellum very small, with a discontinuous row of denticles in- side, 1st joint scarcely as long as the other 2 combined, terminal spine nearly as long as the last joint. Colour greyish brown, with more or less distinct, darker brown pigmentary ramifications. Length of adult female 6 mm., of male scarcely more than half that size. Remarks. This is as yet the only known species of the genus, and may be easily recognized, at least in the female sex, by the large size and peculiar shape of the middle segment of the mesosome. Occurrence. I have met with this form not infrequently in several places, both on the south and west coasts of Norway, in depths ranging froir 20 to 30 fathoms, on a muddy bottom covered with decaying alg3. Distribution. British Isles (Robertson), Mediterranean at Messina and Spezia (the present author). Skagerak and Kattegat (Meinert). Tribe k. ASELLOTA. Be-mark*. In the present group of Isopoda all the segments of the meta- some are fused together, forming a more or less broad shield-like plate, the caudal segment. The pleopoda have wholly lost their swimming power, being exclusively branchial in character, and they are moreover considerably reduced in number. In by far the greater number of the forms, the 1st pair are transformed to a single oper- cular plate, to protect the extremely delicate succeeding pairs, this operculum being, in the male, peculiarly modified. The uropoda. as in the group Chelifera, are terminal, never forming part of a caudal fan. nor being valvular in character. Though, as above stated, the appendages of the metasome are quite unserviceable for locomotion, there are some forms belonging to this group, which show them- selves to be very expert swimmers; but the swimming is here effected in a very different manner, vix., by the aid of the 3 posterior pairs of legs, which, in such cases, are found to be peculiarly modified, forming oar-like swimming implements, by the strokes of which, the animal is propelled backwards. This is more par- ticularly the case in one of the families, the Munnopsidce; but some of the Des- mosomidce are also enabled to move in a similar manner, though never so rapidly as the first-named. As to the general form of the body, it is greatly variable, sometimes very broad and depressed, sometimes slender and elongated, approaching to a cylin- drical shape. The cephalon is always well defined, and the mesosome exhibits the nor- mal number of segments, which sometimes arrange themselves with tolerable distinct- ness into 2 sets by a median constriction. The coxal plates are very small or quite obsolete, never forming a marginal area, as is generally the case in the two pre- ceding groups. Of the antenna 1 , the superior ones are generally smaller than the inferior, which sometimes attain an excessive length. The oral parts are, on the whole, normally developed, and of the legs, only the 1st pair sometimes assume a 95 i subcheliform structure. None of the forms belonging to the present group lead a parasitic existence. The group contains as yet 5 families, all of which arc re- presented in the fauna of Norway. It is, however, very probable that it will be found convenient to establish more families subsequently. Fam. 1. Asellidae. Characters. Body more or less broad, depressed, with the lateral parts of the segments lamellar. (Vphalon of moderate size, without any rostrum, lateral parts scarcely expanded. Caudal segment large, shield-like. Eyes, when present, small, lateral. Both pairs of antenna 1 with multiarticulate flagella, the superior ones much smaller than the inferior, and issuing close together. Oral parts nor- mal. Legs ambulatory, except the 1st pair, which are distinctly subcheliform. Pleopoda in female 4 pairs, the 1st being very small, not operculiform, consisting each of a single rounded lamella; the 3 succeeding pairs biramous, with both rami lamelliform, outer lamella of 2nd pair very large and incrusted, so as to form, together with the corresponding lamella of the other side, a sort of oper- culum, completely covering the 2 succeeding pairs. Pleopoda in male 5 pairs, an additional very small pair, constituting the copulative appendages, being inter- posed between the 1st and 2nd. Uropoda comparatively large, biramous, with the rami styliform or lamellar. Remarks. In the restriction here adopted, this family is chiefly charac- terized by the structure of the pleopoda, which differs considerably from that found in the other Asellota, Whereas in these, the 1st pair in the female are invariably transformed to a single large opercular plate, completely covering the succeeding pairs, this pair, in the forms belonging to the present family, are of inconsiderable size and not at all opercular, forming 2 discrete, simple, setiferous lamellae. On the other hand, the outer plate of the 2nd pair is very large and incrusted, lying in close contact with that of the other side, so as to obtect completely the 2 succeeding pairs. In the male, there is found, immediately behind the 1st pair of pleopoda, an additional pair of very small biramous appendages, of which no trace can be detected in the female, and which represent the copulative organs. As regards the other Asellota, the male operculum is apparently split into 3 juxtaposed segments, one narrow median segment, which exhibits a well-marked 96 suture along the middle, and 2 lateral segments of a more or less oval form, and carrying inside 2 peculiar movable appendages (see PI. XL and succeeding). A closer examination of this compound operculum will, however, soon show, that the suggestion at first put forward by Dr. Hansen is quite correct. According to the opinion of this distinguished carcinologist, the male operculum is more properly composed of 2 pairs of successive appendages; the median piece repre- senting the 1st pair of pleopoda, and accordingly answering to the female oper- culum. whereas the lateral pieces represent the copulative appendages peculiar only to the male. By such an explanation, indeed, more uniformity is obtained, as to the number of appendages of the metasome, which, in fact, is the very same in all Asellota, viz., 4 pairs in the female, and 5 pairs in the male, the additional pair constituting the copulative appendages. In any case, however, the structure of the 2 first pairs in the forms here treated of, is very anomalous, and the remaining pairs are also rather different in appearance from those in other Asellota, thus justifying the establishment of a distinct family. This family comprises as yet 4 genera, viz.. AscUu*. Mancasellus, Ccecidothea and Stenetrium, all, except the last-named, containing exclusively fresh-water species. Of these 4 genera, only the first is represented in the fauna of Norway. Gen. AsellUS, G. St. Hillaire, 17(34. Generic Characters. Body broad, depressed, with the lateral parts of the segments simple, not laciniate. Cephalon not very large, rounded, truncated in front, lateral faces convex. Caudal segment very broad, slightly produced at the tip. Eyes, when present, very small, consisting of a limited number of visual elements. Superior antenme scarcely longer than the peduncle of the inferior ones, the latter slender and elongated, without any outer appendage to the pe- duncle. Mandibles with a well developed palp, molar expansion thick, subcylindric in form. Second pair of maxilla 1 with the outer lamella? broad, laminar, and edged with numerous curved and coarsely denticulated spines. Maxillipeds having in female at the base a posteriorly pointing setous lappet, epignath broad, edged witli bristles. 1st pair of legs with the carpus very small, propodos much larger and broader in male than in female. The succeeding pairs rapidly increasing in length, and having the carpal joint well developed, propodal one linear, dac- tylus spinulose inside. Uropoda with the rami subequal, slender, styliform. Remarks. This genus was established as early as in the year 1764 by Geoffroy St. Hillaire. and may accordingly be regarded as the type of the family. 97 From the nearly-allied genus Mane .iselliis Harger it is prominently distinguished, among other things, by the presence of well-developed mandibular palps. Five species of this genus have been recorded, only one of which belongs to the fauna of Norway. Asellus aquaticus (Lin.). (PL XXXIX.) (htiscus aquaticiis, Linne, Fauna Svecia, ed. 2da, p. 500. S}-n : Sqnilla aselhts, de Geer. Oymothoa aquatica, Fabr. Asellus vulgaris, Latr. IdotJiea aquatica, Latr. Specific Characters. Body oblong oval, in male slightly widening behind, in female with the greatest width about in the middle, and equalling half the length, not including the caudal segment. Cephalon broader than it is long, with a slight setotis prominence on each side near the base, frontal edge straight. Segments of mesosome of nearly uniform size, lateral parts transversely truncated at the tip, and clothed with stiff hairs. Caudal segment about half the length of the mesosome, rounded quadrangular in form, and fringed all round with stiff hairs; terminal edge bisinuate. with an obtuse median prominence. Eyes consist- ing each of only 4 visual elements, ocular pigment not confluent. Superior antennae about the length of the peduncle of the inferior ones, flagellum composed of 10 12 articulations. Inferior antennas not quite as long as the body, flagellum more than twice the length of the peduncle. Legs densely clothed with spiniform bristles; 1st pair rather short, with the propodos in female oblong oval, in male subtriangular, inner edge forming an obtuse prominence, armed with 3 strong spines. Uropoda with the rami more than twice as long as the basal part, and edged with scattered spiniform bristles. Colour very dark, fuscous, spotted with white. Length of adult female 8 mm., of male 12 mm. Remarks. This form has been treated of in detail by the present author in one of his earlier works: "Crustaces d'eau douce de Norvege", to which the reader may lie referred for detailed information on the more minute anatomy and the development. Occurrence. The species would seem to occur everywhere in Norway, especially in small ponds that have a muddy botfflm, and are covered at the sur- face with Lemna. It is also occasionally met with in slow streams, and in larger lakes, but never at any considerable depth. Distribution. The European continent everywhere, Siberia, Algieria (the present author). 13 Crustacea. 98 Fam. 2. laniridae. Characters. General habitus that of the Asettidw, but the lateral parts of the cephalon always lamellarly expanded. Eyes, when present, suhdorsal. Superior antenme sometimes well developed, with the flagellum multiarticulate, sometimes very small, with rudimentary flagellum. Inferior antenna 1 always longer than the su- perior, with the peduncle 6-articulate, and generally carrying a small accessory appendage (scale) outside the 3rd joint. Oral parts normal. Legs subequal in length, with the dactylus generally hi- or tri-unguiculate ; 1st pair sometimes differing from the others in being prehensile. 1st pair of uropoda in female transformed into a single, large, opercular plate, in male constituting the median piece of the compound operculum, the lateral pieces of which are formed by the copulative appendages. The 3 succeeding pairs very delicate, the last pair forming simple smooth lamella?, the 2 preceding ones with the outer ramus narrow and confluent with the basal part. Uropoda biramous, more or less developed. Remarks. The forms belonging to this family resemble the Asellidce very much, as regards their external appearance, and have also hitherto been combined with them. Yet the very different structure of the pleopoda makes it, in my opinion, necessary to place them in a separate family. As additional distinguishing characters may be mentioned the laterally-expanded cephalon, the subdorsal situation of the eyes, the distinctly 6-articulate peduncle of the inferior antenna 3 , on which, in the greater number of the forms, a small outer appendage, apparently answering to the scale in higher Crustacea, may be distinguished; finally, the more uniform length of the legs, the dactylar joint of which moreover, as a rule, is hi- or tri-unguiculate. All the known forms are exclusively marine, and, as it were, replace the Asell'ulce in the Oceans. Several genera have been established, amounting to 9 or 10 in all, 4 of which only are represented in the fauna of Norway. Gen. 1. lanira, Leach, 1813. Syn: (hilsroda, Ln.tr. Hmopomus, Kroyer. Asellodes, Stimpson. Generic Characters. Bo Aj oblong, depressed, with the lateral parts of the segments but slightly produced. (Vphalon large, transversely oval, obtuse in front, or with a comparatively small rostral projection. Caudal segment rounded. 99 not expanded laterally. Eyes distinct, subdorsal. Superior antennee well deve- loped, with the tiagellum composed of numerous short articulations carrying long olfactory filaments. Inferior antennae very much elongated, with a well-marked scale-like appendage outside the 3rd joint of the peduncle. Mandibles with the cutting part divided from the molar expansion by a deep incision, palp rather slender. Second pair of maxillre with the outer lobes narrow, conic in form, and tipped by a limited number of simple seta3. Maxillipeds normal. Legs nearly equal in length, 1 st pair of same structure in the 2 sexes, prehensile, the carpus being very large, subfusiform, and edged inside with spines, propodos narrow, linear, and very movably articulated to the former, so as to admit of being bent in against it, dactylar joint in all legs very small, 3-unguiculate. Uropoda largely developed, with the rami slightly unequal, and clothed with fasciculated bristles. Remarks. This genus was established as early as in the year is 13 by Leach. The genera Oniscoda of Latreille, and Axdlodes of Stimpson, as also that of Heiiopomus Kroyer, are all undoubtedly identical with the Leachian genus, which, as the much older one, ought to be retained. It is the type of the family lanir'vla 1 , and the genus which in external appearance exhibits most re- semblance to the fresh-water genus Asdlus. Five species have as yet been re- corded, viz., 2. maculosa Leach, /. tricornis Kroyer, I. alta Stimpson, I. alnjssorum Beddard, and /. Tristani Beddard. Of these, only the first-named belongs to the fauna of Norway. lanira maculosa, Leach. (PI. XL.) Syn: Oiiisrorta maculosa, M.-Eihv. Henopomus wuticiis, Kroyer. Specific Characters. Body oblong oval in form, about 3 times as long as it is broad, and slightly narrowed both in front and behind. (Vphalon with the lateral expansions evenly rounded, frontal edge straight, without a trace of rostrum. Anterior segments of mesosome with the lateral parts slightly produced at both corners, but not covering the small coxal plates, which are bi-lobulate. Caudal segment sub-circular, distal part of lateral edges coarsely serrated. Eyes well developed, rounded oval, with dark pigment. Superior antenna' reaching ahout to the end of the penultimate peduncular joint of the inferior ones, tiagellum more than twice as long as the peduncle, and composed of about 30 articulations. In- ferior antennae considerably exceeding the length of the body, the last 2 pedun- cular joints rather elongated, subequal, flagellujn about twice the length of the U)0 peduncle. Kpignath of the maxillipeds with the outer edge angular in the middle. 1st pair of legs with the carpus about the length of the 2 preceding joints coin- Lined, and armed inside with 18 20 spines; dactylar claws in all pairs nearly equal. Middle piece of male operculum not expanded at the end, which is qua- drilobate. Uropoda exceeding in length the caudal segment, basal part rather elongated, though not quite as long as the inner ramus, outer rainus somewhat smaller than the inner, both being linear in form. Colour yellowish, densely mottled with reddish brown specks. Length of adult female 7 mm., of male 10 mm. Remarks. This is the first described species of the genus, and is easily recognizable from the other as yet known forms, by the form of the cephalon and the armature of the caudal segment. The Henopomus muticus of Kroyer is un- doubtedly identical with the form here treated off. Occurrence. This species occurs along the whole Norwegian coast, from the Christiania Fjord to Vadso, and is generally found in depths ranging from 30 to 100 fathoms, on a rocky bottom, overgrown with Hydroida and Polyzoa. It is rather brittle, and therefore difficult to preserve in a perfect state. The long inferior antenna and the uropoda are especially liable to be broken or de- tached from the body, when the animal is put in alcohol. Distribution. British Isles (Sp. Bate), Kattegat (Meinert), Dutch coast (Hoek), coast of France (Bonnier), Greenland (Hansen). Gren. 2. lanthe, Bovallius, 1881. Generic Characters. General form of body as in lanira. Cephalon with a strong rostral projection, and having the lateral parts produced to very pro- minent, acute lappets. Segments of mesosome with the lateral parts laciniate, and produced so as wholly to cover the coxal plates. Caudal segment forming at the end, on each side, a triangular expansion. Antennae about as in lanira, except that the inferior ones are comparatively less elongated. Epignath of maxillipeds simple lanceolate, outer edge not angular. Oral parts otherwise, as also the legs and appendages of metasome, nearly as in lanira. Remarks. This genus was established in the year 1881 by Dr. Bovallius, to include a supposed new species from Baffin's Bay, I. speciosa, which, however, in the opinion of Dr. Hansen, is not specifically distinguishable from lanira of Harger. The genus agrees very closely in almost all anatomical details 101 with Jni/ir/i, ;nul it is therefore somewhat questionable, whether it can in reality be maintained. As, however, there are at least 3 species, which closely agree in the distinguishing characters recorded by Dr. Bovallius for his genus, 1 am un- willing at present to reject it, lanthe laciniata, G. 0. Sars. (PL XLI.) Ifinira laciniata, G. 0. Sars, Bidrag til Kundskaben oni Dyrelivet pan vore Havbanker, Chr. Vid. Selsk. Forli 1872, p. 92. Specific Characters. Body much flattened, oval in form, being scarcely twice as long as it is broad. Cephalon provided with a long, spiniform, somewhat upturned rostrum, lateral parts each produced to a strong lanceolate lappet point- ing obliquely anteriorly. Segments of mesosome with the lateral parts laminarly expanded, and each produced into 2 lanceolate lappets separated by a deep incision, those of the 4 anterior segments subequal, those of the 3 posterior ones rather unequal, the anterior lappet being much the larger. Caudal segment much broader than it is long, gradually widening behind, and produced at the end, on each side, to an acute triangular expansion, median prominence blunted, all the lappets finely serrated at the edges, and, like the dorsal face, clothed with scattered hairs. Eyes comparatively small, rounded. Superior antennae reaching somewhat beyond the penultimate peduncular joint of the inferior ones, flagellum about twice the length of the peduncle, and composed of 20 30 articulations. Inferior antennae scarcely longer than the body, squamiform appendage of the peduncle distinctly developed, flagellum not quite twice as long as the peduncle. Legs almost exactly as in lanira maculosa, except that one of the dactylar unguiculi is much smaller than the other 2, and somewhat remote from the tip of the dactylus. Middle piece of male operculum very slightly expanded at the end, which is irregularly serrulated, with a small hamiform projection on each side. Uropoda fully as long as the caudal segment, and densely clothed with spiniform bristles, inner ramus scarcely as long as the basal part, outer ramus a little shorter, both being narrow linear in form. Colour pale yellowish white, semipellucid, without any pigmentary ornament. Length of adult male 8 mm. Remarks. This form was first recorded by the present author in 1872 as lanira laciniata. It is nearly allied to the North American species, I. spinosci Harger, but differs in the greater development of the lateral lacinise, as also in the shape of the caudal segment. Occurrence. I first met with this pretty form outside the Storeggen bank, where 2 specimens were brought up in the dredge from the considerable depth 102 of 400 fathoms. Subsequently I have found it occasionally off the coasts of Xordland and Finmark, in depths ranging from 100 to 150 fathoms. Out of Norway it has not yet been recorded. Gen. 3. lanlPOpSiS, G. 0. Sars. n. Generic, Characters. General habitus that of Ian int. Lateral parts of the segments but slightly expanded, not laciniate. Eyes well developed. Superior antennse comparatively small, with the rlagellum only composed of a limited number ot articulations. Inferior antennae of moderate length, being much more strongly O \J built in male than in female; squamiform appendage in both sexes very small, but distinctly denned. Maxillipeds with the 2nd and 3rd joints of the palp very much expanded, laminar. Legs comparatively short and thick, with the dactylus bi-unguiculate ; 1st pair in female not differing at all from the others, in male, on the other hand, remarkably developed, prehensile, much longer than any of the other pairs, with the carpal joint fusiformly dilated. Middle piece of male oper- culum remarkably dilated at the tip. Uropoda of same structure as in lauint, but much shorter. Remarks. This new genus is founded upon the form recorded by the present author as lanlra breviremis. A closer examination of this form, and more especially of the male, has revealed some characteristic features, which make it advisable to separate it generic-ally from lanint, and such a separation was also opined by Dr. Bovallius to be necessary. It is especially the structure of the 1st pair of legs which is characteristic. In the female, this pair, unlike what is the ease in lanira, do not differ in any manner from the others legs, being, like these, ambulatory. On the other hand, this pair assumes in the male a quite extra- ordinary development, being pronouncedly prehensile, and much larger than any of the other legs. Moreover, the structure of the superior antenna- and the maxillipeds is slightly different, as also the middle piece of the male operculum. The genus contains as yet but a single species, to be described below. laniropsis breviremis, G. 0. Sars. (PI. XLII.) laiiira brcriremis, G. O. Sars, Oversigt at' Norge.s Crustaceer I, p. H4. PI. 2, fig. 4. Specific Characters. Body oblong oval in form, fully twice as long as it is broad, and very slightly narrowed both in front and behind. Cephalon rather in:; large, subquadrangular, lateral parts but slightly expanded, frontal edge trans- versely truncated. Segments of mesosome with the lateral parts bluntly truncated. Caudal segment circular in outline, lateral edges serrated, tip bluntly produced. Eyes rather large, rounded oval. Superior antennae scarcely reaching beyond the middle of the penultimate peduncular joint of the inferior ones, nagellum but little longer than the peduncle, and composed in female of 8, in male of 12 articula- tions. Inferior antenna? in female not nearly attaining the length of the body, in male considerably larger, equalling the body in length. 1st pair of legs in female a little shorter than the next succeeding, but of the very same structure; those of male more than twice as large, almost attaining the length of the whole body, carpal joint oblong fusiform and, like the other joints, densely clothed with short spiniform bristles. Middle piece of male operculum produced at the end. on each side, to a lanceolate lappet minutely bind at the tip. Uropoda much shorter than the caudal segment, and clothed with scattered fascicles of spiniform bristles, inner ramus somewhat longer than the basal part, outer, considerably smaller. Body yellowish, mottled everywhere with reddish brown specks. Length of adult female 4 mm., of male 6 mm. Remarks. As above stated, this is as yet the only known species of the genus, and may easily be recognized from lanira maeulosa, to which it bears some resemblance in colour and external appearance, by the comparatively much shorter antenna? and uropoda. Occurrence. I have only met with this form off the west coast of Norway, in the neighbourhood of Bergen. In one locality, at Bratholmen, it occurred in considerable numbers on the roots and stems of Laminarise overgrown by Hydroida and Polyzoa. Distribution. Bohuslan (Bovallius). Gen. 4. laera, Leach, 1813. Syn: laerldina, M.-Edw. Generic Characters. Body, as a rule, broad and much depressed, with the lateral parts of all the segments laminarly expanded and fringed with bristles. Cephalon broad, without any true rostrum, but with the lateral parts considerably produced. Caudal segment with a more or less deep apical emargination, within which the uropoda are contained. Eyes distinct, dorsal. Superior antenme ex- tremely small, with the tiagelliim rudimentary. Inferior antenna? of moderate 104 length, without any distinctly defined squamiform appendage. Oral parts nearly as in lanira. Legs comparatively short and of uniform structure, the 1st pair not being prehensile in either sex, dactylar joint 3-unguiculate. Middle piece of male operculum considerably expanded at the end. Uropoda extremely small, bi- ramous, rami very short, nodiform. Male smaller than female. Remarks. This genus, established by Leach in the year 1813, is chiefly distinguished by the short and flat body, the very small superior antejmre and uropoda, and the uniform structure of the legs. It comprises as yet about 7 species, only one of which belongs to the fauna of Norway. laera marina (Fabr.). (PI. XLIII.) Omscus marinns, O. Fabvicius, Fauna Gronlandic-a, p. 252. Syn : laera albifrons, Leach. Eroyeri, Zaddacli. laltlca, Fr. Miiller. copiosa, Stimpson. nil-alls, Kroyer. Specific Characters. Pody oval in form, scarcely more than twice as long as it is broad, in male somewhat shorter and stouter than in female, and slightly widening behind, lateral edges of the segments in both sexes fringed with rather short and simple hair-like bristles. Cephalon more than twice as broad as it is long, lateral expansions obliquely truncated, frontal edge slightly Insinuate, obtusely produced in the middle. Caudal segment semicircular in shape, comparatively larger and broader in male than in female, apical notch not very deep. Eyes of moderate size, rounded oval in form. Superior antenna? reaching but little beyond the antepenultimate peduncular joint of the inferior ones, flagellum very small, bi- nrticulate. Inferior antennae about the length of the body, not including the cau- dal segment, outer appendage of the peduncle replaced by a simple spine, fla- gellum fully twice as long as the peduncle. Legs but slightly increasing in length posteriorly, one of the 3 dactylar claws rather small, and somewhat removed from the tip. the other 2 strongly curved. Female operculum semicircular; middle piece of male operculum forming at the end, on each side, a rather large expan- sion terminating in a hook-like, anteriorly-curving point. Uropoda projecting somewhat beyond the apical notch of the caudal segment, both rami well defined, though very small, and tipped by a fascicle of bristles, the inner one about half the length of the basal part, the outer considerably smaller. Body more or less thickly dotted with dark brown, sometimes uniformly blackish or variegated with large whitish patches. Length of adult female 4 mm., of male 3 mm. 105 Remarks. By most authors, this form has been recorded under the spe- cific name albifrons, proposed by Leach; but as there cannot be any doubt that the Oniscus marinus of 0. Fabricius is this species, the latter specific name, as the older one, ought to be preferred to that of Leach. Four more synonyms are quoted above. The laera Nordmanni Rathke, of which I have had specimens for examination from the Caspian Sea, is a very nearly-allied species, but is distinguished pretty well by the dense and regular garniture of spiniform bristles, and by the still more poorly developed uropoda, the rami of which look merely like small setiferous noduli. It seems to me somewhat doubtful whether the form figured by Sp. Bate and Westwood under this name, is the true Rathkian species, or perhaps more properly the male of /. marina. Occurrence. This species occurs along the whole coast of Norway, from the Christiania Fjord to Vadso, in quite shallow depths. At low water, it is often found in great numbers beneath stones on the beach, and sometimes at a consider- able height above the level of the sea, together with Ligia oceanica and other terrestrial Isopoda. Its flat body makes it admirably well adapted to cling to the stones of the beach, andto conceal itself in their crevices. Distribution. -British Isles (Sp. Bate), Kattegat (Meinert), Dutch coast (Hoek), coast of France (Bonnier), Greenland (Hansen), Atlantic coast of North America (Harger). Fam. 3. Munnidae. Characters. Body generally diort and stout, with the 3 posterior segments of mesosome, as a rule, sharply marked off from the 4 anterior, and much smaller. Caudal segment more or less vaulted above, sub-pyriform. Eyes, when present, placed on the tips of lateral, peduncle-like projections of the head. Superior an- tennae placed widely apart, and more or less developed, with the flagellum gene- rally multiarticulate. Inferior antenna? issuing immediately beneath the superior, and without any outer appendage. Oral parts normal. 1st pair of legs much shorter than the others, prehensile; the succeeding pairs more or less rapidly in- creasing in length, simple, ambulatory. Uropoda generally small, somewhat re- moved from the tip of the caudal segment, being sometimes subdorsal. Male much smaller than female. 14 Crustacea. 106 Remarks. The type of this family is the peculiar genus Mnnna of Kroyer, with which several other genera may be conveniently associated, to form a rather well-defined group of Ascllota. From the laniridw, these Isopods may be easily distinguished by the comparatively short and stout body, which, unlike the body in that family, is conspicuously narrowed behind, with the 3 posterior segments of the mesosome much smaller than the 4 anterior ones, and the caudal segment ob-pyriform in shape. Besides the 4 Norwegian genera treated of below, the following genera may with certainty be referred to this family: Leptaxpidia Bate & Westw., NeaseUus Beddard, Astrurus Beddard, Munnclla Bonnier, and Haliacris Pfeffer. The last-named genus, however, is, scarcely different, generic- ally, from Munna. Gen. 1. Munna, Boeck, 1839. ? Syn: Haliacris, Pfeffer. Generic Characters. Body sub-pyriform in shape, with the dorsal face some- what vaulted, and the last 3 segments of mesosome very small, with the lateral parts curving more or less posteriorly. Cephalon very broad, with the frontal margin obtusely produced. Caudal segment narrow, ob-pyriform, and very sharply defined from the mesosome. Eyes distinct, placed on the tips of greatly produced lateral projections of the head. Superior antenna 1 comparatively small; inferior antennae, on the other hand, very much elongated, with the peduncle 5-articulate, the 2 outer joints long and slender. Mandibles with the cutting part divided from the cylindrical molar expansion by .a deep incision, palp well developed. 1 st pair of legs in female comparatively small, imperfectly subcheliform, in male more strongly developed, and sometimes of quite an extraordinary size. The re- maining legs rapidly increasing in length, with the carpal and propodal joints much elongated and edged with spines, dactylar joint small, bi-unguiculate. Middle piece of male operculum rather narrow, snblinear. truncated at the tip. Uropoda very small, simple. Remarks. This genus was established by Kroyer in the year 1839, to include a peculiar Tsopod found by him off the Norwegian coast. Subsequently several additional species were detected by different authors, and the relation of this genus to other Isopoda was more fully recognized. The external appearance is rather peculiar, the apparently stalked eyes especially being very striking. In ovigerous females, moreover, owing to the greatly projecting incubatory pouch, the fore-part of 107 tin- body appears less depressed than in most other Isopods. and, as the very much elongated legs in alcoholic specimens are generally stretched downwards, the body, unlike that of other Isopods, presents itself to the observer, as a rule, in u lateral position. We know of 9 or 10 species of the genus, 5 of which belong to the fauna of Norway, and will be described below. l. Munna Boecki, Kroyer. (PL XLIV.) Munna Boeckii, Ki-oyer, Nat. Tidsskr. Bd. II, p. 612, PI. VI, figs. 19. Specific Character*. Body of female very short and thick, with the an- terior division, seen from above, almost circular in outline; last segment of meso- sonie very small. Caudal segment about half the length of the anterior division of the body, ob-pyriform, lateral edges somewhat bulging in their anterior part, and each armed with 4 short denticles, tip obtusely produced, and exhibiting ventrally, on each side of the anal orifice, a coarsely serrated lamella. Eyes rather large, semiglobose. Superior antenna- scarcely reaching to the middle of the penultimate peduncular joint of the inferior ones, iiagellum composed of 6 articulations, the apical one being extremely small. Inferior antennae moderately strong, about twice the length of the body, flagellum somewhat longer than the peduncle. Legs rather strongly built, and rapidly increasing in length posteriorly; 1st pair with the carpus gradually widening distally, and armed inside with a double row of slender spines, propodos oval inform. Last pair of legs exceeding the body in length, carpal joint about the length of the 3 preceding joints com- bined, and rather strong, widening distally, propodal joint long and slender, linear. Uropoda very small, with the tip transversely truncated. Colour yellowish, very slightly clouded with darker shadows. Length of adult female 4 mm. Remarks. This is the species first recorded, and ought accordingly to be regarded as the type of the genus. It may be easily recognized from the other species by the very broad, nearly circular fore-part of the body, the form and armature of the caudal segment, the comparatively large eyes, and the long, but rather strongly built legs. Occurrence. I have met with this form occasionally in a few localities on the west coast of Norway, in depths ranging from 20 to 50 fathoms, on a rocky bottom, overgrown with Hydroida and Polyzoa. Kroyer observed the species at Trondhjem. Kattegat (Meinert). 108 2. Munna limieola, G. 0. Sars. (PI. XLV, fig. 1.) Munna limieola, G. O. Sars, Beretning 0111 en i Sommeren 1865 foretagen zoologisk Beise ved Kj'sterne af Christianias og Christiansands Stifter, p. 29. Specific Characters. Body of female somewhat less robust than in the type species, with the anterior division oval in form. Ocular processes very much projecting. Caudal segment rather large, nearly equalling the mesosome in length, and oval pyriform in shape, lateral edges evenly curved, and without any den- ticles, but clothed with scattered bristles, tip without any serrated lamellae. Eyes comparatively smaller than in M. BoecM, and narrowly rounded. Superior antennae reaching to the middle of the penultimate peduncular joint of the inferior ones, flagel- lum 5 -articulate, last articulation, as usual, extremely small. Inferior antennae twice the length of the body, flagellum much shorter than the peduncle. Legs greatly increasing in length posteriorly, and far less strongly built than in M. BoecJci; 1st pair with the carpus but slightly widening distally, and nearly as long as the propodos; last pair considerably exceeding the body in length, and having the carpal joint rather narrow, propodal joint extremely slender, being almost twice as long as the former. Uropoda nearly as in the type species. Colour uniformly pale yellowish grey. Length of adult female 3 mm. Remarks. Though rather nearly allied to M. Boecki, this species may, on a closer examination, be easily distinguished by its less robust body, the smaller eyes, the form of the caudal segment, and the absence on it of lateral denticles and apical serrated lamell*, and finally, by the extremely slender and elongated legs. Occurrence. This species occurs not infrequently both off the south and west coasts of Norway, from the Christiania Fjord, at least to the Lofoten Islands. It is only found in greater depths, ranging from 60 to 300 fathoms, on muddy bottom. Out of Norway, it has not yet been recorded. 3. Munna Fabricii, Kroyer. (PL XLV, fig. 2.) Munna Fabricii, Kroyer, Nat. Tidsskr. Bd. 11, p. 380. Specific Characters. Body rather short and compact, with the anterior divi- sion rounded oval in outline. Ocular processes rather thick, and less prominent than in M. limieola. Caudal segment oblong oval, but slightly narrowed behind, lateral edges evenly convex, and each armed in front with a single slender den- ticle; apical lamellae distinctly serrated. Eyes rather large, semi-globose. Supe- rior antennae scarcely reaching to the middle of the penultimate peduncular joint 109 of the inferior ones, flagellum composed of only 4 joints, including the very small apical one. Inferior antenna) rather slender, with the flagellum longer than the peduncle. Legs comparatively slender, though less rapidly increasing in length posteriorly than in the 2 preceding species; 1st pair, as usual, much the shortest, with the carpus somewhat shorter than the propodos, and armed inside with 3 spines; last pair scarcely longer than the body, carpal joint somewhat dilated distally. Uropoda obliquely truncated at the tip, and setous at each corner. Colour dark brown, from numerous pigmentary spots forming irregular shadows. Length of adult female scarcely reaching to 3 mm. Remarks. This species was established by Kroyer from Greenland spe- cimens; but its true specitic characters were not fully recognized. For the figures given by the same author in the great work of Gaiinard, evidently belong to two distinct species, confounded by him at that time. From the 2 preceding species, it may be distinguished by the comparatively more slender inferior antenna?, the less elongated legs, and the form and armature of the caudal segment. It is also rather inferior in size, and always exhibits a very dark colour. Occurrence. The species is rather common off the Lofoten Islands and along the whole Finmark coast, in moderate depths, among Hydroida. It also occurs occasionally off the west coast of Norway, but nowhere in any abundance. Distribution. Greenland (Kroyer), Atlantic coast of North America (Harger), Iceland and Spitsbergen (Norw. North Atl. Exped.). 4. Munna Kroyeri, Goodsir. (PI. XLVI, tig. 1.) Munna Kroyeri, Goodsir, Edinb. New Phil. Journ. Vol. XXXIII, p. 365, PL 6, fig. ti. Syn: Munna Whiteana, Sp. Bate & Westw. $. Fabricii, Kroyer (part). Specific Characters. Body of female somewhat robust, with the anterior division oval in form, and the segments very sharply marked off from each other, and clothed laterally with scattered hairs. Body in male, as usual, much narrower. Ocular processes conically tapered. Caudal segment comparatively short, scarcely more than half as long as the uiesosome, and rounded oval in form, lateral edges rather bulging in front, and each armed with 4 strong denticles, the posterior pair subdorsal, tip bluntly produced, and without any serrated lamellae. Eyes comparatively small, at least in female. Superior antennae very short, extending not nearly to the middle of the penultimate peduncular joint of the inferior ones, flagellum composed of only 3 articulations, including the very small apical joint. 110 Inferior antenna?, as compared with those in the other known species, of incon- siderable length, scarcely as long- as the body, rlagellum not attaining the Jength of the peduncle. 1st pair of legs in female of the usual structure, in male con- siderably stronger, with the carpus considerably expanded, and produced at the end inside to an acute thumb-like projection, the inner edge of the joint densely setiferous. Ambulatory legs in both sexes shorter and stouter than usual, last pair scarcely exceeding in length the anterior division of the body. Uropoda produced at the tip into several dentiform projections, one of which 'assumes a hook-like appearance. Colour pale yellowish, slightly mottled with light brown. Length of adult female about 3 mm. Remarks. This form was h'rst described by Goodsir from male specimens. The female was subsequently recorded by Sp. Bate and Westwood as a new species under the name of J/. Whltcana. Kroyer confounded the species with his M. Fabricii, a fact wJiicli may easily be proved on examining the several figures he gives in the work of Gaimard. Indeed, the greater number of these figures evidently belongs to the present species, and not to M. fahricii. The present form may be easily distinguished from any of the preceding species by the com- paratively short and stout inferior antenna? and legs, as also by the peculiar structure of the uropoda. The caudal segment, moreover, differs both in shape and armature from that in the said species. Occurrence. I have found this form occasionally off the south and west coasts of Norway, in comparatively shallow water. Distribution. British Isles (Goodsir, Sp. Bate), Kattegat (Kroyer)?. 5. Munna palmata, Lilljeborg. (PI. XLVl, fig. 2.) MHIIIKI pnhnnta, Lilljeborg, Ofvers. Vetensk. Akad. F<">rhunMnnna, though not sufficient to admit of its beilig combined with that genus. It seems also to be rather nearly allied to the genus Lcptaspidia of Sp. Bate & Westwood, though differing very prominently in the presence of well-developed, pedunculated eyes, and in the uropoda being biramous, not simple. We know, as yet, of only a single species, to be described below. 112 Paramunna bilobata, G. 0. Sars. (PI. XLVII, fig. 1.) Paramunna bilobata, G. 0. Sars, Beretning om en i Sommeren 18H5 foretagen zool. Keise ved Kysterne af Christianias og Christiansands Stifter, p. 31. Specific Characters. Body oval in form, scarcely twice as long as it is broad, with the segments very sharply marked off from each other. Cephalon rather broad, deeply incised anteriorly in the middle, and forming on each side of the incision an obtusely truncated lobe finely denticulated at the tip ; ocular processes conical and greatly projecting. Lateral parts of the 4 anterior segments of mesosome trun- cated at the tip; those of the 3 posterior acuminate and projecting laterally. Caudal segment about half as long as the mesosome, rounded cordiform, lateral edges rather bulging in front, and each armed with a regular row of about 12 strong serrations increasing in size posteriorly, outer part of the segment obtusely conic and smooth. Eyes well developed, and placed on the tips of the ocular processes. Superior antennae projecting laterally between the cephalic lobes and the ocular processes, and equalling in length about half the breadth of the head, the first 2 joints of the peduncle rather large, subequal, 3rd joint extremely small, flagellum nearly as long as the peduncle, and composed of 3 articulations, the last carrying a single long apical filament. Inferior antennee extending beyond the superior, and nearly twice as long, flagellum much shorter than the pe- duncle, and 7-articulate. 1st pair of legs very strongly built, with the joints con- siderably expanded, carpus rather broad, and armed inside with 3 strong spines, propodos about the size of the carpus, and oval in form, dactylus strong, with a secondary tooth inside. Uropoda issuing just behind the serrated part of the lateral edges of the caudal segment, rami very unequal, the outer one being ex- tremely small. Colour bright red. Length of adult female scarcely exceeding 1 mm. Remarks. This dwarfed Isopod may be easily recognized from the other Munnidce by its rather regular oblong oval body, the peculiar form of the cepha- lon, and the shape and armature of the caudal segment. The distinct, peduncu- lated eyes distinguish it at once from the species of the nearly-allied genera, Leptaspidia, Neasellus and Pleurogonium. Occurrence. I have met with this form occasionally in several places of the Norwegian coast, from the Christiania Fjord up to the Lofoten Islands. It generally occurs in moderate depths ranging from 20 to 40 fathoms, among Alga? and Hydroidse, more rarely in greater depths amounting to 100 fathoms. Owing to its small size, it may easily be overlooked, or taken for some Copepods of the Scntellidian group. Out of Norway it has not yet been recorded. 113 Gen. 3. PleurOgOIlium, G. 0. Sars. Syn: Pleuracantha, G. 0. Sars (olim). Generic Characters. Body short, depressed, with the 4 anterior segments of mesosome more or less strongly dilated, the 3 posterior ones much smaller, and having the lateral parts obliquely recurved. Cephalon comparatively smnll, deeply sunk within the 1st segment of mesosome, and without any frontal lobes or ocular processes. Caudal segment narrowly cordate or pyriform, constricted at the base, tip more or less produced. Eyes wholly absent. Antennae differing but little in size, and of a structure similar to that in Paramunnn. Mandibles without palps, cutting part narrowly produced, molar expansion slender, lappet- shaped. 1st pair of legs short and strong, subcheliform ; the others slender, in- creasing in length posteriorly. Female operculum lanceolate, male, of a simi- lar structure to that in Paraminma. Uropoda very small, biramous, placed somewhat dorsnlly, and at a considerable distance from the tip of the caudal segment. Remarks. This genus was established by the present author in the year 1863; but the name Plcuracantlia, proposed at that time, having been already appropriated, he changed it subsequently to Pleurogonium. The genus is nearly allied to Paramnnna, but differs very markedly in the shape of the cephalon and caudal seg- ment, as also in the absolute want of eyes and of mandibular palps. In addition to the 3 Norwegian species described below, Mr. Beddard lias recorded 3 other species from the Challenger Expedition as P. allidum, serration and inmuhim. 1. Pleurogonium rubieundum, G. 0. Sars. (PI. XLVII, fig. 2.) Pleuracantlia rubicnnda, G. 0. Sars, Om en anomal Gruppe af Isopoder (Chr. Vid. Selsk. Forli. 18H3), p. Iti. Specific Characters. Anterior division of body in female nearly circular in outline, the breadth almost equalling the length. Cephalon sub-pentagonal in form, with the front obtusely produced, and the sides obtusangular. Lateral parts of the 4 anterior segments of mesosome subangular, and each carrying in the middle a very conspicuous rod-like spine, all the spines pointing in different directions, so as to exhibit a radiating arrangement. The 3 posterior segments of mesosome very small, with the lateral parts extended obliquely behind, and each terminating in a knob-like projection. Caudal segment rather narrow, con- siderably constricted at the base, side-edges evenly curved, and fringed with short 15 Crustacea. 114 hairs in their outer part, tip obtusely pointed. Superior antennae exceeding in length the breadth of the cephalon, 1st joint of the peduncle rather elongated, Hagellum scarcely longer than that joint, and composed of 3 articulations. Inferior antenna} but little longer than the superior, and of the structure characteristic of the genus; flagellum 7-articulate. 1st pair of legs with the carpus strongly dilated distally, being considerably broader than it is long, and armed inside with 2 strong spines, anteriorly with 2 smaller ones ; propodos oblong oval, exceeding the carpus in size; dactylus strong, with 2 small denticles inside. Ambulatory legs about of same structure as in Paramunna lilobata. Middle piece of male oper- culum likewise rather similar, though comparatively smaller. Uropoda with the outer ramus extremely small. Colour bright red. Length of adult female 1 ! /a mm. Remarks. This is the species first recorded, and it may accordingly be regarded as the type of the genus. It is easily recognized from the other 2 Norwegian species by the peculiar rod-like spines radiating from the sides of the fore-part cf the body. Occurrence. The species occurs along the whole Norwegian coast, from the Christiania Fjord to Vadso, and is often found in considerable numbers on a muddy bottom, in depths ranging from 6 to 30 fathoms. It is a rather sluggish animal, creeping slowly along the bottom, and is often so thickly covered with muddy particles as only with great difficulty to be discerned. Out of Norway, it has not yet been recorded. 2. Pleurog'onium inerme, G. 0. Sars. (Pi. XLVIIt, fig. 1.) Pleurogonium inerme, G. O. Sars, Oversigt at' Norges Crustaceer I, p. t>7, PI. 2. fig. 5. Specific Clutrfirtrrx. Very like the preceding species, but without a trace of the rod-like lateral spines characteristic of that form, the lateral parts of the segments being only obtusely angular. Cephalon somewhat less produced in front, and almost twice as broad as it is long. Caudal segment comparatively larger and broader than in the type species, obcordate in form, tip pointed. The several appendages of the body nearly exactly as in P. rubicundum. Colour pale greyish, with a very faint reddish tinge. Length of adult female about 2 mm. Remarks. The present form is so very like the preceding one, that at first I only regarded it as an accidental variety. Having, however, subsequently found it in several places, and of pretty constant appearance, I am now of the opinion that it represents a distinct, though very closely allied species. It is 115 best recognized hy the absolute want of lateral spines, and . the pale colour of the body. Occurrence. Though nowhere in any abundance, I have met with this form in several places on the west coast of Norway, and always in rather con- siderable depths, ranging from 60 to 150 fathoms. Distribution. British Isles (Kobertson), Kattegat (Meinert). 3. Pleurogonium spinosissimum, G. 0. Sars. (PI. xLvm, fig. y.) Plewacantlia spinosissima, G. 0. Sars, Beretning oni en i Soinmeren 1865 fovetagen zool. Keise ved Kysterne af Christianias og Christiansands Stifter, p. 30. Specific Characters. Body oblong oval in form, slightly tapering posteriorly. Cephalon blunted in front, and slightly eniarginated on each side at the insertion of the superior antennce. Lateral parts of the 4 anterior segments of mesosome irregularly angular, and each projecting into 2 diverging serrated processes, the anterior of which more properly represents the produced coxal plate of the cor- responding segment. The 3 posterior segments of mesosome, as usual, much smaller than the anterior, and each having laterally a single strong, serrated spine, likewise representing the produced coxal plate. Caudal segment rather large, obcordate, lateral edges considerably bulging in the middle and densely hairy in their outer part, tip acutely produced. The several appendages of the body resembling in structure those in the 2 preceding species, excepting that the female operculum is comparatively much broader and very acutely produced at the tip. Colour bright red. Length of adult female 3 mm. Remarks. This is a very distinct species, easily recognizable from the other known forms by the coarse armature of the body, which, indeed, has given rise to the specific name. It is also of considerably larger size. Occurrence. I have found this pretty species occasionally in several lo- calities of the Norwegian coast, from the Christiania Fjord to Yardo, in depths ranging from 50 to 100 fathoms. Distribution. British Isles (Robertson), Kattegat (Meinert). 116 Gen. 4. DendrOtlOn, G. O. Sara, 1871. Generic Characters. Body resembling somewhat in shape that in Pleuro- goninm, being much depressed, with the anterior part of the mesosome rather broad, and flanked by strong spines, the posterior abruptly narrowed, with lingtii- form produced lateral parts. Cephalon comparatively small, and produced on each side to a remarkable ear-like projection carrying the antennae. Caudal segment very narrow, lanceolate. Eyes absent. Antennae long and slender, especially the inferior ones, the peduncle of which is 5-articulate. Mandibles normal, with well- developed palp and molar expansion. Legs extremely slender, and rapidly in- creasing in length posteriorly; 1st pair rather feeble in structure, though distinctly subcheliform. Uropoda issuing from the dorsal face of the caudal segment, rather elongated, biramous, outer ramus very small, inner long and narrow. Remarks. The present genus is founded upon a very peculiar deep-water Isopod, which, though in some points differing rather markedly from the other Mttn- nid(8, yet undoubtedly is referable to that family. The most striking feature is the insertion of the antennae to ear-like processes of the head, which character indeed has given rise to the generic name. Another very anomalous character, which was not fully recognized at first, is the great development and peculiar origin of the uropoda, in which respect this genus differs very materially from all other known Munnidce. Dendrotion 1 ) spinosum, G. 0, Sars. (PL XLIX.) Dendrotion spinosum, G. O. Sars, Undersogelser over Hardangerfjordens Fauna. I. Crustacea, pag. 30. Specific Characters. Body oblong fusiform in outline, more than twice as long as it is broad, with the segments very sharply marked off from each other. Cephalon comparatively small, sub-quadrangular, slightly widening distally, frontal edge evenly concave, antennal processes obliquely diverging and truncated at the tip. Anterior division of mesosome ob-ovate, gradually widening posteriorly, lateral parts of the segments angular, and each produced into a strong and very acute spine, pointing straight outwards and clothed at the base with scattered hairs. Posterior division of mesosome abruptly narrowed, with the lateral parts of the segments linguiformly produced, and decreasing in size posteriorly, each terminating in a sharp spiniform point, hairy at the base. Caudal segment l ) By a mistake, the generic name, in the plate, is spelt Pleurotion instead of Dendrotion. Idotheidas. I s op o da- i. 33. G. 0. S ars, autogr . Idothea pelagica, Leach . IdoiheidaB. I s op o da__ PI. 34-. G.O. S ars, autogr . 1. Idothea granulosa, Rathke 2. ., angusta , n . sp. Idotheidae I s op o da. PI. 35. G. 0. S ars, autoqr . I. Idothea neglects, n.sp. 2. emarqinata, Leach Arciuridaa. I s opo da. PI. 36 G.O. S srs, autogr Astacilla longicornis , ( Sowb.). Arciuridae. I s op o da.. PI. 37. G.O.Sars, autogr. 1. Astacilla arietina G.O.Sars, 2. affinis , G.O.Sars 3 pusilla, G O.Sars. Arcturidae. I s op o da.. PI. 38. j ) y, ( L f-L /fl ' Mi ' I G.O. S ars, autogr Arcturella dila-tata, G .0. Sars . A s e 1 1 i d se . I s op o da.. PI. 39 G. 0. S ars, autogr Asellus ac^vaticus , Lin . Janiridse. I s op o da. PI. 40. G.O. S srs, autogr . lanira maculosa, Leach, laniridae. I s op o da- . 41 GO. S ars, autogr lanihe laciniata , G.O. Sars laniridas. I s op o da.. PI. 42 G. 0. S ars, autogr . laniropsis breviremis, G.O. Sars laniridce. I s op o da. PI. 43. G.O. S srs, autogr . laera marina (Lin.) Munnids. Is op o da.. PI. 44. G.O.S ars, autogr Munna Boecki, Kroyer. I s op o da. PI. 45. G.O. S ars, autoqr 1. AAunna limicola, G.O.Sars 2. Fabric!!, Kroyer. Munnidas- I s op o _L PI. 46, G.O. S ars, autogr I. Munna Kroyeri, Goodsir. Palmata, Lilljeb. Munnidae . I s op o PI. 47. G.O. S ars, autogr . I.Paramunna bilobala , G.O.Sars . 2. Pleurogonium rubicundum ,G.O. Sars, Munnidae. I s opo da- i. 48. G. 0. S ars, autogr . 1. Pleurogonium inerme , 6. 0. Sars. 2. , spinosissimum, G.O.Sars. 117 slender and elongated, nnrrow lanceolate in form, and strongly constricted at the base, lateral edges slightly curved, and each armed in the middle with 4 short denticles, tip acutely produced. Superior antennae not quite half the length of the body, 1st joint of the peduncle exceeding in length the other 2 combined, and clothed with very strong, scattered bristles, 2nd joint very small, 3rd linear, flagellum nearly as long as the peduncle, and composed of 10 articulations, the outermost of which carry delicate olfactory filaments. Inferior antennse about twice the length of the superior, the 2 outer joints of the peduncle slender and elon- gated, flagellum shorter than the last peduncular joint, and composed of about 16 articulations. 1st pair of legs rather small, carpus scarcely at all dilated, propodos about as long as the carpus, and oblong fusiform, with a few spines inside. The other legs very slender, and clothed with scattered spiniform bristles; last pair nearly equalling the body in length, and having the propodal joint ex- tremely slender and elongated; dactylus in all pairs simple, conically tapered. Female operculum narrow lanceolate, with 2 apical setre; middle piece of male opcrculum not expanded distally. Uropoda issuing close together from 2 juxta- posed obtuse prominences of the dorsal face of the caudal segment, and consider- ably exceeding it in length, basal part long and narrow, outer ramus small and turned inwards, inner ramus very much elongated, linear, and, like the basal part, edged with scattered, slender bristles. Colour whitish grey. Length of ad- ult female 2 mm. Remarks. This is as yet the only known species of the genus, and is easily recognizbale from any of our other Isopoda, exhibiting, indeed, a very bizarre appearance. The exact length of the uropoda cannot be stated, as in the solitary specimen possessing them, the outer part of the inner ramus was broken off. On the whole, all the appendages are extremely brittle, and, indeed, in none of the specimens examined, were they preserved in an entire state. Occurrence. The only place where I have met with this peculiar form, is in the outer part of the Hardanger Fjord, at Mosterhavn, where a few speci- mens were detected on a close examination of a quantity of sandy clay taken up by the, aid of the dredge from a depth of 150 fathoms. Out of Norway, this form has not yet been recorded. 118 Fam. 4. Desmosomidae. Characters. Body more or less elongated, with the segments, as a rule, sharply marked off from each other, the 3 posterior segments of mesosome gener- ally defined from the 4 anterior by a well-marked constriction. Cephalon emar- ginated on each side for the insertion of the antenna;, frontal part more or less produced. Caudal segment generally rounded at the tip. Eyes wholly absent. Superior antennae, as a rule, small, and placed wide apart. Inferior antennae not particularly elongated, sometimes different in the 2 sexes. Mandibles with or without palps. Maxillipeds always lamellar, with the joints of the palp more or less expanded. 1st pair of legs generally unlike the others, prehensile or very slender. The 3 posterior pairs of legs in some cases natatory, with the outer joints flattened, but never, as in the Munnopsidce, edged with ciliated seta;. Uro- poda generally small, bi- or uni-ramous. Remarks. The present family is somewhat intermediate in character between the Icmiridos and Munnopsidce, some of the forms resembling the former, others the latter family. I have, however, thought it advisable to keep it apart from both of them. All the known forms are blind, and generally have the body narrow and elongated, with the segments, as a rule, very sharply marked off from ea'-li other, so as to exhibit a more or less moniliform shape. The family com- prises as yet 6 genera, all of which are represented in the fauna of Norway. Gen. 1. NannOniSCUS, G. O. Salts, 1S69. Generic 0/um/rfox Body distinctly depressed, with the segments rather densely crowded together, and lamellarly expanded laterally. Cephalon compara- tively large, with the frontal part considerably produced. Caudal segment like- wise larger than usual, semi-oval. Superior antemue extremely small, with the peduncle apparently only consisting of 2 joints, tiagellum rudimentary, and carrying outside a single, enormously developed olfactory papilla. Inferior antenme of moderate size, with the peduncle 6-articulate, its 3rd joint being produced outside to a strong, anteriorly pointing spine. Mandibles with the molar expansion rather slight, conical, and tipped by a fascicle of slender bristles; palp distinct, 3 -arti- culate, though not very large. Maxillipeds pronouncedly lamellar, penultimate joint of the palp produced at the end inside to a digitiform process; epignath 110 lanceolate, pointing anteriorly. Legs, at least in female, of uniform structure, simple, ambulatory, but slightly increasing in length posteriorly, dactylus bi- unguiculate. Uropoda issuing from the ventral face of the caudal segment, com- paratively small, biramous, raini linear. Remarks. The systematic position of this genus is somewhat doubtful. In several characters, for instance the total absence of eyes, the structure of the oral parts, and partly also of the caudal appendages, it certainly agrees per- fectly with the other Desmosomidce ; but the general form of the body is some- what different, and the structure of the antenme and legs resembles more that in the laiilrida?, and perhaps therefore it should more properly be included in that family. Besides the type species described below, another nearly-allied species has recently been detected in the Caspian Sea (N. cn^this G. 0. Sars). On the other hand, the form described by the present author from the Norwegian North Atlantic Expedition as N. bicuspis, is scarcely congeneric, differing, as it does, considerably, in the structure of both the antenme and the oral parts, and also in that of the caudal appendages. Nannoniscus oblongus, G. 0. Sars. .(PL L.) Nannoniscus oblmiijns, G. 0. Sars, Nyc Dybvandscrustaceer t'ra Lot'ntcn. Chi-. Vid. Sflsk. Fnrh. 18(59, p. 164. Characters. Body of female rather regularly oblong oval, nearly o times as long as it is broad, and but very slightly narrowed behind; that of male with the posterior division, comprising the last 3 segments of mesosome and the caudal segment, much narrower than the anterior. Cephalon in both sexes very large, with the lateral parts projecting, outside the antennae, to an acute, anteriorly pointing corner, frontal part very prominent, and minutely incised at the tip. Lateral parts of the 4 anterior segments of mesosome projecting in front as acute lappets; those of the 3 posterior segments subtruncate and quite contiguous. Caudal segment larger in female than in male, being in both sexes semi-oval in outline, with the tip evenly rounded. Superior antenna' scarcely extending beyond the tip of the frontal part, 1st joint rather thick, 2nd of about the same length, but much narrower, tlagellum extremely small, its olfactory papilla very large, almost globular. Inferior antenme of essentially same structure in the two sexes, scarcely attaining half the length of the body, spine of the 3rd peduncular joint of mo- derate length and pointing slightly outwards, tiagelluni slender 8 10-articulate. 1st pair of legs in female of the very same structure MS the others, in male, how- 120 ever, rather different, and very strongly built, prehensile, carpus considerably ex- panded, and armed inside with 2 long spines, propodos oblong oval, with a strong spine inside, dactylus strong and curved. Female operculum with a spiniform projection near the base; that in male simple, not transformed as in other Asellota. Genital prominence in male very large, spiniform, recurved, issuing from the ventral face of last segment of mesosome, immediately in front of the operculum. Uropoda in both sexes of the same appearance, projecting but slightly beyond the edge of the caudal segment, outer ramus considerably smaller than the inner, Colour whitish, semipellucid. Length of adult female 2 mm., of male iy 2 mm. Remnrl-x. This form was first described by the present author only from female specimens. The male, of which 2 specimens were found subsequently among the females, looks so very different, that at first I was in some doubt of its belonging to the same species. After having examined more closely the several appendages, I cannot, however, doubt that it is in reality the male of the present species. The 1st pair of legs are certainly very different; but this may be merely a sexual character; for in all the other appendages, the resemblance to the female is very close. It is a very remarkable fact, that the operculum in neither of the 2 specimens examined showed any trace of the usual transformation, though the male character of the specimens otherwise could easily be demonstrated, both by the greatly projecting sexual prominence, and by the presence of well-developed testes shining distinctly through the integuments in their usual place. In the Caspian species, on the other hand (of which as yet only a solitary male specimen is known), the sexual characters were quite normally displayed. Occurrence. I have as yet only found this form off the Lofoten Islands, at Skraaven, in depths ranging from 120 to 250 fathoms. Out of Norway, it has not yet been recorded. Gen. 2. MacrOStyllS, G. O. Sars, 1863. Syn : Vana, Meinert. Generic Characters. Body narrow, sublinear, with the 3 posterior seg- ments of mesosome very sharply marked off from each other, the 4 anterior more densely crowded together. Cephalon rather large, subtriangular, frontal part con- siderably produced. Caudal segment oblong, obtusely produced at the tip. Supe- rior antennae extremely small, with the ilagellum rudimentary. Inferior antennae slender, with the peduncle 5 -articulate, and the flagellum well developed. Man- dibles of a similar structure to that in the genus Nannoniscus, but without any trace of palp. Maxillipeds with the 2 outer joints of the palp rudimentary. Legs rather unequal; the 2 anterior pairs of essentially the same structure, not prehensile; 3rd pair much more strongly built, and apparently fossorial in character ; the 4 posterior pairs very slender and rapidly increasing in length. Female oper- culum very narrow ; male operculum transformed in the usual manner. Uropoda very slender, styliform, simple, bi-articulate and greatly divergent. Remarks. This genus was established by the present author as early as in the year 1863, to include a very peculiar, small Isopod from the Christiania Fjord. The genus Vana of Meinert is unquestionably identical with the present genus. In the structure of the legs and uropoda, this genus differs rather con- spicuously from the other Desmosomidce, though it evidently ought to be referred to that family. Only a single species is as yet known. Macrostylis spinifera, G. 0. Sars. (PI. LI.) Macrostylis spinifera, (Jr. O. Sars, Oni en anonial Gruppe af Isopoder. Clir. Vid. Selsk. Forhandl. 1863, p. 15. Syn: Vana longiremis, M-;inert. Specific Characters. Body oblong, semicylindric in form, being more than 4 times as long as it is broad. (Jephalon rather broad at the base, and very slightly sinuated on each side for the insertion of the antennce, frontal part con- siderably produced, and obtusely rounded at the tip. The 4 anterior segments of mesosome with the lateral parts scarcely at all expanded; 3rd segment the lar- gest; 4th segment terminating on each side in a posteriorly-pointing spine. The 3 posterior segments of mesosome much narrower than the anterior, and sepa- rated by deep constrictions, lateral parts obliquely expanded, and terminating in a short pointed projection. All the segments of mesosome, except the 1st, produced ventrally to strong spiniform processes. Caudal segment nearly as long as the 3 posterior segments of mesosome combined, oblong pyriform in shape, with a slight notch on each side, at some distance from the tip, the latter obtusely produced. Superior antenna scarcely extending beyond the frontal part of the head, 4-arti- culate, the last articulation representing the rudimentary nagellnm. Inferior an- tennae, when reflexed, extending about to the end of the 4th segment of mesosome, penultimate peduncular joint the longest, flagellum shorter than the peduncle, and 7-articulate. 1st pair of legs of nearly exactly the same structure as the 2nd, though having the carpus comparatively shorter; 3rd pair much more strongly built, and generally extending laterally, ischial joint produced outside, beyond the 1C Crustacea. 122 middle, to a strong, recurved, spiniform process, meral joint forming at the end, outside, a lamellar expansion clothed with a dense row of slender spines, carpal joint carrying in the distal part of the outer edge 4 similar spines, propodal joint, 'as in the 2 preceding pairs, short and simple, forming together with the dactylus an elongated claw. The 4 posterior pairs of legs much more slender than the anterior, and edged with scattered spines ; the anterior pair very small ; the last 2 pairs greatly elongated and nearly equal; dactylus in all of them small and simple, tipped with 2 bristles. Female operculum keeled along the middle, tip narrowly rounded, and, like the lateral edges, densely setous. Copulative ap- pendages of male comparatively narrow, with the digitiform process very much elongated and almost straight. Uropoda fully as long as the caudal segment, narrow linear, distal joint scarcely more than half as long as the proximal one. Colour whitish. Length of adult female 2*/2 mm., of male 2 mm. Remarks. This form is easily recognizable from any of our other Isopoda, both by its outward appearance, and by the structure of the several appendages. Though the description and figure given by Prof. Meinert of his V. Generic Characters. Body extremely narrow, with the 4th and 5th seg- ments of mesosome firmly connected, and together forming a slender hourglass- slinpcd section, carrying at each end the corresponding legs. Cephalon compara- tively small, and deeply immerged within the 1st segment of mesosome. Caudal segment not very large, constricted at the base. Superior antenna 1 more fully developed than in the other J>/'6mosomid(e, with the flagellum distinct. Inferior an- tenna' long and slender, and of same structure in the two sexes. Mandibles without palps, molar expansion well developed, cylindric. Penultimate joint of the pal}) of the maxillipeds not produced at the tip. First pair of legs in both sexes prehensile, witli the carpus greatly expanded; the other pairs simple, am- 123 bulatory, and very much elongated, terminating in a slender claw. Uropoda of moderate length, simple, Inarticulate. Remarks. This is a very distinct genus, exhibiting in some characters an approach to the genus Desmosoma, though being well distinguished, among other things, by the non-natatory character of the posterior pairs of legs, and by the peculiar appearance of the 4th and 5th segments of the mesosome. The genus comprises as yet 5 species, 3 of which (I. spinosum, bacillus and bacilloides) have been described by Mr. Fr. Beddard from the Challenger Expedition, the other 2 being northern forms. Of these the one (I. quadrispinosum, Gr. 0. Sars) was procured during the Norwegian North Atlantic Expedition, the other belongs to the fauna of Norway, and will be described below. Ischnosoma bispinosum, CI. 0. Sars. (PI. LII.) Ischnosoma bispinosum, G. 0. Sars, Beretning om en i Sommeren 1865 foretayen zool. Reise ved Kysterne af Ghristianias og Christiansands Stifter. p. )54. Specific Characters. Body sublinear in form, more than 5 times as long- as it is broad, the greatest width occurring far in front. Cephalon sub-quadrang- ular in outline, very slightly notched on each side for the insertion of the antennae, frontal part obtusely truncated. 1st segment of mesosome deeply emarginated in front, lateral parts produced to obliquely anteriorly pointing spiniform projections more prominent in male than in female. Middle section. comprising the firmly connected 4th and 5th segments of mesosome, about half the length of the body, and pronouncedly hourglass-shaped, being in male ex- tremely narrow in the middle. The last 2 segments of mesosome very short. Caudal segment oval in form, gradually widening somewhat distally, tip evenly rounded. Superior antennae reaching beyond the middle of the penultimate pe- duncular joint of the inferior ones, 1st joint very short, 2nd long and slender, with 3 remarkably strong seta? inside, 3rd half the length of the former, fiagellum 3-articulate. Inferior antennae fully as long as the body, the outer 2 joints of the peduncle long and slender, edged with scattered bristles, Hagellum about the length of the peduncle, and composed of numerous (about 20) articulations. 1st pair of legs much shorter than the others, and pronouncedly prehensile, carpus greatly expanded, exhibiting a well-defined palm armed with several short den- ticles, and, at the lower corner, a slender spine. The remaining legs of exactly the same structure and very slender, terminating in a long and narrow claw. Copulative appendages of male rather broad, with the digitiform process quite 124 short. Uropocla scarcely exceeding half the length of the caudal segment, proxi- mal joint projecting at the end, outside, to a strong spine, distal joint somewhat shorter, and tipped with a dense fascicle of delicate bristles. Colour whitish, semi-pellucid. Length of adult female 3 mm., of male 2 ! /2 mm. Remark*. This is the species first recorded, and ought accordingly to he regarded as the type of the genus. It is easily distinguished from the 2nd northern species, I. quadrispinosum, by the fact that only the 1st segment of the mesosoine is produced on each side to spiniform projections, whereas in the latter species this is also the case with the 2nd segment. Occurrence. Besides in the Christiania Fjord, where this form was first detected, I have found it occasionally in several other localities of the Norwegian coast, as far north as the Lofoten Islands, the depth ranging from 50 to 250 fathoms. It is very brittle, the antennae and legs especially being very liable to be broken off, so that it is very unusual to get a specimen with all its appen- dages uninjured. Distribution. Skagerak, off the Skagen Light House (Meinert). Gen. 4. DeSlTLOSOma, G. O. Sars, 1863. Generic Characters. Body slender, sublinear, slightly depressed, with the 2 divisions of mesosoine sharply marked off from each other. Cephalon of mode- rate size, slightly notched on each side for the insertion of the antenna?, frontal part obtusely produced. The 4 anterior segments of mesosome of nearly uniform size, and having the lateral parts more or less produced in front; the 3 posterior segments much flattened, with the lateral parts lamellarly expanded. Caudal seg- ment not very large, semi-oval. Superior antennae comparatively small, with the last peduncular joint not sharply defined from the flagellum. Inferior antennae in female slender, though not particularly long, in male much more strongly built, with the 2 outer joints of the peduncle considerably tumefied, and the fla- gelluin fusiform, being dilated in its proximal part, and densely clothed in front with delicate sensory hairs. Oral parts of almost exactly the same structure as in the genus Nannoniscus. 1st pair of legs more or less strongly built, though scarcely subcheliform ; the 3 succeeding pairs subeijual and densely clothed with spines. The 3 posterior pairs of legs of a rather different appearance, natatory, the outer joints being compressed and edged with flattened, unciliated spines, 125 dactylus styliform. Female operculum rounded, without any longitudinal keel; male operculum transformed in the usual manner. Uropoda not very large, simple, Inarticulate, distal joint much larger than the proximal one. Remarks. This genus was established by the present author as early as in the year 1863, and was at that time included within the group "Isopoda remi- gantia", answering to the now generally accepted family Munnopsidce. The reason for this was that the 3 posterior pairs of legs were proved to act as pulling implements, by which the animal is enabled to move freely through the water in a backward direction. In their structure, however, these legs differ rather pro- minently from those in the true Munnopsidce, and in most other characters this genus resembles much more closely the 3 preceding genera, and may therefore more properly be associated with them in a separate family. In the restriction here adopted, the genus comprises as yet only 3 species, 2 of which will be de- scribed below, the 3rd having recently been recorded by M. Jules Bonnier from the Bay of Biscay under the name of IJ. elongatum. 1. Desmosoma lineare, G. 0. Sars. (PI. LIII, PL LIV, fig. 1.) Desmosoma lineare, G. 0. Sars, Om en anomal Gruppe af Isopoder. Chv. Vid. Selsk. Forhandl. 1863, p. 11. Specific Characters. Pody slender, linear in form, being in female almost 5 times as long as it is broad, in male somewhat shorter. Cephalon of moderate size, irregularly rounded, frontal part somewhat produced, and transversely trun- cated in female, slightly insinuated in male. The 4 anterior segments of mesosome differing but little in shape, lateral parts in all of them curving anteriorly, and terminating in an acute corner, which in male is produced to a strong spiniform projection. Posterior section of mesosome exceeding in length the preceding part of the body, and fully as broad, in male even somewhat broader, 1st segment large and expanded, with the antero-lateral corners acutely produced. Caudal segment in female semi-oval, in male broader, almost semicircular, edges evenly curved. Superior antenna? 6-articulate, 2nd joint the longest. Inferior antenna? in female scarcely longer than the anterior division of the body, last joint of the peduncle longer than the penultimate one, flagellum about the length of those joints combined, and composed of 12 14 articulations. Inferior antenna? in male considerably larger, attaining half the length of the body, 2nd joint of the pe- duncle armed outside with a strong spine, the 2 outer joints considerably tume- fied, and each having 2 spines at the end outside, flagellum pronouncedly fusi- 126 form, with the proximal joints rather incrassated. 1st pair of legs moderately strong, slightly attenuated, carpus not dilated, and only clothed inside with scattered bristles, propodos narrow, suhlinear. The 3 succeeding pairs very densely clothed with spines arranged on the outer Joints in a double row, dactylus com- paratively small. The 3 posterior pairs of legs successively somewhat diminishing in size, basal joint large and muscular, meral joint very small, triangular, carpal joint large, oblong, compressed and edged inside with a regular row of flattened spines successively increasing in length dis tally, and more numerous in male than in female, propodal joint oblong lamelliform, and likewise, fringed with slender spines, dactylus slender, styliform, with 3 sub-apical bristles. Uropoda somewhat exceeding half the length of the caudal segment, distal joint sublinear, 4 times as long as the proximal one. Colour whitish, semi-pellucid. Length of adult female 3 l /% mm., of male 2 mm. Remarks. The present species may be regarded as the type of the genus, and is easily distinguished from the succeeding one by the fuller development of tiie 3 posterior segments of the mesosome, as also by the structure of the 1st pair of legs, and the shape of the caudal segment. Occurrence. The species occurs along the whole south and west coasts of Norway, from the Christiania Fjord at least to the Lofoten Islands, and is found in depths ranging from 30 to 100 fathoms. The animal being extremely fragile, only imperfect specimens are generally procured by the aid of the ordinary dredge. To catch it in an uninjured state, very delicate dredging implements are required, and it is indeed by such means that I have succeeded in getting many Crustacean forms, which otherwise would have escaped my attention. The swimming motion of the animal has the character of a quite even run through the water in a back- ward direction. During this run, the 3 posterior pairs of legs are seen to be in a rapid vibrating motion, whereas the anterior pairs are extended in front. At other times the animal is seen creeping slowly along the bottom in the or- dinary manner. Out of Norway, this form has not yet been recorded. 2. Desmosoma armatum, G. 0. Sars. (I'l. LIV, fig. 2.) Desmosoma armatum, U. 0. Sars, Om en anoiiial Gruppe af Isopoder. Clir. Vid. Selsk. Forhl. 1863, p. 12. Specific Characters. Body comparatively less slender than in the preced- ing species, with the posterior division considerably narrower than the anterior 127 and scarcely exceeding it in length. Cephalon rather large, with the frontal part narrowly truncated. First segment of mesosome scarcely smaller than the suc- ceeding ones, and produced on each side to an acute, anteriorly-pointing lappet; lateral parts of the 3 succeeding segments evenly rounded ; 5th segment with the antero-lateral corners not produced. Caudal segment oblong oval in form, with a distinct notch on each side near the tip. Superior antennae 5-articulate. In- ferior antennae about half the length of the body, flagellum not attaining the length of the 2 outer peduncular joints combined, and composed of 8 articulations. 1st pair of legs very strongly built, carpus large and broad, with 4 slender spines inside, propodos about the same length, but narrower, and oblong oval in form. The 3 succeeding pairs of legs narrower than in D. linear e, and less densely clothed with spines ; the 3 posterior pairs likewise considerably narrower than in the type species, though otherwise of a very similar structure. Uropoda scarcely more than half the length of the caudal segment, distal joint about 3 times as long as the proximal one. Colour whitish, semi-pellucid. Length of adult female scarcely 2 mm. Bernards. The present species, of which only female specimens have hitherto come under my notice, is easily distinguishable from I), lineare by the less fully developed posterior section of the mesosome, the form of the 1st seg- ment and of the caudal segment, and the very strongly built 1st pair of legs. Occurrence. I have met with this form occasionally in 2 widely distant localities of the Norwegian coast, viz., in the inner part of the Christiania Fjord and at Aalesund, the depth ranging from 30 to 50 fathoms. Out of Norway, it has not yet been recorded. Gen. 5. Ellgerda, Mi-inert, 1890. Syii : Desmosoma, G-. 0. Savs (part). Generic Characters. Form of body much as in Desmosoma ; 1st segment of mesosome, however, very small, and not produced laterally in any of the sexes. Antenna? and oral parts of almost exactly the same structure as in the said genus. 1st pair of legs in both sexes very slender and feeble, with the outer joints ex- tremely narrow, almost filiform ; the other legs of a similar structure to those in Desmosoma. Uropoda distinctly biramous, outer ramus smaller than the inner. Remarks. This genus was established in the year 1890 by Prof. Meinert, to include a supposed new Isopod from Kattegat, which, however, has turned out 128 to he identical with a form previously described hy the present author as a species of the genus Desmosoma. Though this form on the whole agrees very closely with the 2 above-described species, yet there are at least 2 characters, in which it differs very markedly, viz.. the structure of the 1st pair of legs and that of the uropoda, and for this reason I think it right to maintain the genus proposed by Prof. Meinert, the more so as I have found it advisable to raise another species, previously referred by me to the genus Desmosoma, to the rank of a distinct genus. Eugerda tenuimana, G. 0. Sars. (PI. LV.) Desmosoma Icniiliitauum, G. 0. Sars, Beretiiing om en i Sommeren 18(55 foretagen zool. Reise ved Kysterne af Christianias og Christian sands Stifter, p. 33. Sj'n : Eugerda ylobiceps, Meinert. Specific Characters. Body slender and elongated, more than 4 times as long as it is broad, with a very conspicuous constriction between the 2 sections of mesosome. Cephalon of a similar form to that in Desmosoma lineare, though comparatively somewhat larger. Anterior section of mesosome about the length of the first 2 segments of the posterior combined, and, in female, "somewhat broader than the latter; 1st segment in both sexes much smaller than the 3 suc- ceeding ones, which are produced on each side to acute anteriorly-pointing lappets assuming in male a spiniform appearance. The 3 posterior segments of mesosome laminar, sub-quadrate in outline, and somewhat broader in male than in female; antero-lateral corner of 5th segment not produced. Caudal segment in female oval, narrowly rounded at the tip, in male almost quadrate in outline, tip blunted, lateral corners rectangular. Superior antennce 6-articulate. Inferior antennas in female very slender, considerably exceeding half the length of the body, flagellum about the length of the peduncle, and composed of about 16 articulations; those in male transformed in a manner similar to that in the male of Desmosoma lineare, though less strongly built: 2nd joint of the peduncle armed outside with a single spine, 4th joint with 2 successive spines, last joint unarmed and considerably larger than the penultimate, flagellum but slightly tumefied in its proximal part. 1st pair of legs very slender and elongated, carpus and propodos extremely nar- row and perfectly smooth ; the 3 succeeding pairs densely clothed with slender spines arranged in a double row ; the 3 posterior pairs of nearly exactly the same structure as in Desmosoma lineare. Uropoda with the inner ramus linear, and about 3 times as long as the basal part, outer ramus not attaining half the length 129 of the inner. Colour whitish, semi-pellucid. Length of adult female 4 mm., of male 3 mm. Remarks. The present form was first described by the present author as Desmosoma tenuimanum, and at the same time the anomalous characters of this species were pointed out. The Eugerda globiceps of Meinert is unquestionably the same species, and accordingly only the generic name proposed by that author ought to be retained. In outward appearance, it bears a great resemblance to Desmosoma lineare, but may, on a closer examination, be easily distinguished by the more elongated inferior antennae, the extremely slender 1st pair of legs, and the distinctly biramous uropoda. Occurrence. This species was first detected at Langesund, south coast of Norway, and I have subsequently found it, though rather sparingly, in the inner part of the Christiania Fjord, at Drobak, as also in the Trondhjem Fjord. Distribution. Skagerak and Kattegat (Meinert). Gen. 6. EchinOpleura, G. 0. Sars, n. Sj'n: Desmosoma, G. O. Savs (part). Generic Characters. Body slender, attenuated, and abruptly narrowed in the middle, 4th and 5th segments of mesosome forming together, as in the genus Ischnosoma, an hour-glass-shaped section. Caudal segment deeply constricted at the base. Lateral parts of all the segments coarsely denticulated. Antennae of a similar structure to that in the 2 preceding genera. Mandibles without palps, cutting edge in the right mandible simple, in the left very slightly bifid, molar expansion extremely small, dentiform, tipped by a single bristle. 1st pair of legs but slightly differing from the 3 succeeding ones, all 4 pairs rather slender, and edged with scattered spiniform bristles; the 3 posterior pairs still more slender, imperfectly natatory, though approaching in structure those in the 2 preceding genera. Uropoda simple, Inarticulate, distal joint the larger. Remarks. The present new genus is established, to include the rather anomalous form previously described by the present author as Desmosoma acti- leatum. On a closer anatomical examination of this form, I have found it to differ in some points so materially from the 2 other species of Desmosoma, that it should more properly be regarded as the type of a separate genus, in some respects exhibiting some resemblance to the genus Ischnosoma. The structure of 17 Crustacea. 130 the mandibles, in particular, is very different from that in the other Desmosomidw. The genus comprises as yet but a single species, to be described below. Echinopleura aeuleata, G. 0. Sars. (PL LVI.) Desmosoma aculeatmn, G. 0. Sars, Om en anunial Grnppe af Isopoder. Clir. Vid. Selsk. Forlil. 1863, p. 13. Specific Characters. Body slender, moniliform, about 4 times as long as it is broad, anterior division much broader than the posterior, and oval in form. Cephalon comparatively large, and very distinctly notched on each side, frontal part in female broadly truncated, in male narrower and distinctly insinuated at the tip, edges of the lateral notches strongly denticulate. Lateral parts of the 4 anterior segments of mesosome with about 6 strong serrations, anterior edge, except in the 1st segment, with a dense row of minute denticles; 4th segment abruptly narrowed behind, and firmly connected with the 5th, both together form- ing an hour-glass-shaped section, about as long as the 3 anterior segments com- bined. The 2 posterior segments of mesosome deeply constricted at the base, and gradually widening behind, lateral edges, as in the preceding segment, coarsely and regularly serrated throughout. Caudal segment oval in form, deeply con- stricted at the base, lateral edges coarsely denticulate, tip narrowly rounded. Superior antenme 4-articulate, and carrying a long apical sensory filament. In- ferior antennae in female scarcely exceeding V 3 of the length of the body, flagel- lum shorter than the peduncle, and composed of 8 articulations; those in male transformed in a similar manner to that in the male of Desmosoma, though not much tumefied, peduncle without an}' spines. 1st pair of legs rather slender, but scarcely at all attenuated, basal joint long and narrow, and finely serrated in front, ischial joint exhibiting outside a small spiniforin projection, carpus with 4 slender spines inside, propodos about the same length, but much narrower, simple, cylindric, dactylus rather strong. The 3 succeeding pairs of legs scarcely longer than the 1st, and of a very similar structure, though having the dactylus narrower. The 3 posterior pairs of legs extremely slender, with the outer joints but slightly expanded, and only provided with a very restricted number of spines, dactylus slender, styliform. Uropoda comparatively small, distal joint 3 times as long as the proximal one, and carrying only 4 or 5 bristles. Colour greyish white. Length of adult female 2y 2 mm., of male V/'-> mm. Remarks. This form was described by the present author as early as in the year 1863, as a species of the genus Desmosoma. Its outward appearance is 131 rather peculiar, and somewhat recalls the species of the genus Ischnosoma, but in the anatomical details it approaches more nearly to the genus Desmosoma. The coarse armature of the body will serve for at once distinguishing it from the species of either of the 2 above-mentioned genera. Occurrence. This species was first observed in the inner part of the Christiania Fjord, at a depth of 15 20 fathoms. Subsequently I have found it, also in several other localities of the Norwegian coast, as far north as the Lofoten Islands, but it seems everywhere to be very rare. Out of Norway, it has not yet been recorded. Fam. 5. Munnopsidse. Characters. Body, as a rule, shorter and more compact than in the Desmosoniidce, with the 2 divisions of mesosome very sharply defined. Eyes ab- sent. Superior antenna? with the basal joint remarkably large and broad, flagel- lum generally well developed. Inferior antenna? very much elongated, and of same structure in the two sexes. Oral parts on the whole normal, though the structure of the mandibles is rather different in the different genera. 1st pair of legs generally smaller than the others, but never subcheliform; the 3 succeed- ing ones, as a rule, very much elongated and ambulatory in character. The 3 posterior pairs of legs very unlike the preceding ones, and pronouncedly natatory, the outer joints being lamellarly expanded, and fringed with densely plumose setae. Uropoda small, simple or biramous. Remarks. In the restriction here adopted, this family is prominently distinguished by the peculiar structure of the 3 posterior pairs of legs, which constitute very powerful natatory organs, by which the animal is enabled to move very rapidly through the water in a backward direction. This motion has not, as in certain DesmosomidoB, the character of an even run, hut is effected by sudden jerks, and is, on the whole, much more energetic, a fact easily accounted for by the rather different structure of the natatory legs, and the densely plu- mose setae with which the very much expanded outer joints are fringed. The family comprises at yet 7 genera, 6 of which are represented in the fauna of Norway, and will be treated of below, the 7th genus, Acanthocope, having been established by Mr. F. Bcddard, to include -2 species from the Challenger Expedition. 132 As our knowledge of this peculiar group of Isopoda is of comparatively recent date, it is highly probable, that the number of genera will, in course of time, be considerably increased, and that it will even be found necessary to subdivide this group into several distinct families. Gen. 1. MunnOpSlS, M. Sars, 1860. Generic Characters. Body less compact than in the other genera, with the anterior division much broader than the posterior. Cephalon of moderate size, deeply emarginated on each side for the insertion of the antennas, frontal part narrowly produced. The 4 anterior segments of mesosome transversely ex- cavated dorsally, with the lateral parts obtuse; the 3 posterior segments densely crowded together, and very convex above. Caudal segment comparatively large, oblong oval. Superior antennas with the basal joint very large and massive, flagellum multiarticulate and much longer in male than in female. Inferior antennas with the 2 outer joints of the peduncle greatly elongated. Mandibles without any molar expansion, cutting edge but slightly dentated, palp well developed, with the terminal joint lamellar, incurved. Maxillipeds pronouncedly laminar, with the antepenultimate joint of the palp acutely produced inside, the 2 outer joints narrow and simple. The first 2 pairs of legs of essentially the same structure, though somewhat different in size; the 2 succeeding pairs extremely slender and elong- ated, with the first 3 joints short and thick. Natatory legs of uniform structure, and rather slender, with the carpal and propodal joints foliaceous and densely edged with plumose setas, dactylus wanting. Female operculum navicular, male operculum transformed in the usual manner, digitiform process of the copulative appendages terminating in a long and slender seta. Uropoda simple, filiform, Inarticulate. Remarks. This genus was established in the year 1860 by my late father, to include a very remarkable Isopod, found by him at Christiansund, west coast of Norway. The generic name refers to a certain resemblance, in outward appear- ance, to the genus Munna of Kroyer. It forms the type of the family Munnop- xiilic, being the first genus recorded, and it is distinguished pretty well from the other genera, both by its outward appearance, and by the structure of the several appendages. In addition to the type species, 4 other species have in recent times been adduced to this genus. Three of these were procured during the Challenger 133 Expedition, and are recorded by Mr. Fr. Beddard as M. gracihs, austmlis and latift'ons; the 4th is described by Dr. Hansen as M. longicornis, from a specimen procured during the German Plankton-Expedition. It is, however, somewhat questionable, if all these species are actually referable to the present genus. Thus, in the species described by Dr. Hansen, the structure of the mandibles is very different from that in Munnopsis typica; and the Challenger species, to judge from the not very exhaustive description given by Mr. Fr. Beddard, seem also to differ very materially in several respects from the type species. Munnopsis typica, M. Sars. (PL LVII & LVIII.) Munnopsis typica, M. Sars, Chr. Vid. Selsk. Porliandl. I860, p. 84. Specific Characters. Anterior division of body in female very broad, rounded in outline, in male somewhat narrower, oval; posterior division very much narrower and longer than the anterior. Cephalon deeply sunk within the 1st segment of mesosome, and provided with 2 juxtaposed tubercles above at the base, frontal part narrowly produced between the bases of the superior antennse, and transversely truncated at the tip. The 4 anterior segments of mesosome separated above by smooth, thin-skinned interspaces, and distinctly excavated trans ver sally, with both the anterior and posterior edges somewhat elevated, lateral parts each with a transversely oval eminence above, those of the 2 posterior segments larger than those of the 2 anterior; coxal plates distinct, though very small. The 3 poste- rior segments of mesosome combined scarcely more than half as long as the an- terior division of the body, and defined by very oblique, arched sutures, the last 2 each having 2 juxtaposed tubercles dorsally, lateral parts narrow, and extended obliquely behind. Caudal segment considerably exceeding in length the 3 preced- ing segments combined, and of narrow oblong oval form, with a single small tubercle above at the base, tip bluntly produced, lateral edges gently curved and perfectly smooth. Superior antenna 1 with the basal joint triangular in outline, inner corner considerably produced, flagellum very slender and composed of numerous short articulations carrying delicate sensory filaments. Inferior antennae more than 4 times as long as the body, flagellum shorter than the peduncle. 1 st pair of legs of same appearance in the two sexes, carpus slightly curved and exceeding the propodos in length, dactylus short; 2nd pair considerably stronger in male than in female, with the carpal joint slightly tumefied and densely armed with short spines inside, dactylus elongated. The 2 succeeding pairs of legs fully 3 times as long as the body, and terminating in a slender claw. Natatory legs 134 with the carpal joint oblong fusiform in outline, propodal joint oval, somewhat shorter, but scarcely narrower. Uropoda about half as long as the caudal seg- ment, distal joint scarcely longer than the proximal one, both being clothed with scattered bristles. Colour pale reddish brown. Length of adult male 11 mm. Remarks. As above stated, this remarkable form was detected by my late father in the year 1860, and was briefly characterised in the above-mentioned journal. Subsequently a fuller description, accompanied by figures, was given in his paper on the fauna of the Christiania Fjord inserted in ,,Nyt Magazin for Naturvidenskaberne". It is much the largest of the Norwegian Munnopsidce. Occurrence. The species occurs along the whole Norwegian coast, from the Christiania Fjord to Vadso, in depths ranging from 60 to 400 fathoms. In some places I have found it in great abundance, especially in the deeper parts of the Christiania and Trondhjem Fjords, as also off the Lofoten Islands. I have several times observed it in a living state, and watched its curious movements. It swims backwards in long, though not particularly rapid bounds, and during this movement the long inferior antennae and the 3rd and 4th pairs of legs are extended straight in front. Immediately on reaching the bottom, the antennae and legs are spread out laterally, and the animal now moves slowly about in the ordinary creeping manner. The appendages are extremely fragile and liable to be broken off from the body, for which reason it is rather difficult to get specimens in quite an uninjured state. Distribution. Skagerak (Meinert), Greenland (Hansen), Spitsbergen (Buch- holt/), the Barents Sea (Hoek), Franz Josef Land (Heller), the Kara Sea (Hansen), Arctic America (Miers), Atlantic coast of North America (Harger). Gen. 2. Ilyaraehna, G. O. Sars, 1863. Syn : Mcsostenus, G. O. Sars (olim). 'H- Churacterx. Body rather compact, clavate in form, attenuated behind, with a very strongly marked median constriction. Cephalon very large and broad, transversely truncated in front, dorsal face evenly vaulted, lateral parts greatly expanded. The 4 anterior segments of mesosome closely crowded together, and slightly excavated transversally ; the 3 posterior segments large and convex above, 5th segment scarcely narrower than the preceding segments, and deeply emarginated behind. Caudal segment narrow, triangular in form. Superior 135 antenna? originating close together from the front, hasal joint large, sub-quadran- gular in form, inner corner somewhat more projecting than the outer, flagellum not much elongated. Inferior antennae exceeding the body in length. Mandibles very massive, with an oblique crest outside, cutting edge undivided, molar ex- pansion narrow, tipped with scattered spines, palp distinct, though rather feeble. Maxillipeds with the 2nd joint of the palp very large and expanded, antepenulti- mate joint rounded at the inner corner, penultimate joint very slightly produced at the end inside, epignath exceedingly large. 1st pair of legs comparatively small, simple; 2nd pair considerably larger and densely edged with spines, dactylus long and slender. The 2 succeeding pairs of legs slender and elongated, with the ischial joint considerably exceeding in length both the preceding and succeeding joints, carpal and prop'odal joints slender, linear, and each having at the end out- side, a very fully developed auditory seta, dactylus long and slender. The 2 anterior pairs of natatory legs of similar structure, with the carpal joint exceed- ingly large and expanded, cordiform in outline, propodal joint much narrower, oblong, dactylus well developed; last pair much narrower than the 2 preceding pairs, with the carpal joint but slightly expanded, propodal joint linear, dactylus much elongated. Female operculum narrow, carinated along the middle, and densely setous at the edges; male operculum transformed in the usual manner. Uropoda comparatively small, Inarticulate, proximal joint lanielliform and edged with cili- ated setae, distal joint very small. Remarks. This genus was established by the present author as early as in the year 1863; but the generic name Mesostenus proposed at that time being already appropriated, it was subsequently changed to Ilyarachna. The genus is easily distinguishable from that of Muitnopsis, both as regards its outward appearance, and the structure of the several appendages. On a closer anatomical examination of the several species previously referred to this genus, I have found it necessary to separate some of them as types of distinct, though nearly-allied genera. In the restriction here adopted, it comprises 3 Norwegian species, to be described below. Moreover, 2 exotic species have been recorded as belonging to this genus, viz., I. quadrispmosa Beddard from the Challenger Expedition, and /. polita Bonnier from the Gulf of Gascogne. Of these, the last-named is unquestionably a true Ilyarachna, whereas the Challenger species seems to differ rather markedly, and should therefore more properly be regarded as the type of a separate genus. 136 1. Ilyarachna longicornis, G. 0. Sars. (PI. LIX.) Mesostenus longicornis, G. O. Sars, Om en anomal Gruppe af Isopodei-. Chr. Vid. Selsk. Forhl. 1863, p. 8. Specific Characters. Body about 3 times as long as it is broad, with the anterior division of uniform width throughout, and about as long as the 3 posterior segments of mesosome combined. Cephalon with the dorsal face perfectly smooth, lateral parts obliquely expanded. The 4 anterior segments of mesosome differing but little in size, being produced on each side to short anteriorly-pointing lappets, anterior edge distinctly elevated and very smooth. Fifth segment of mesosome rather large, being scarcely narrower than the preceding segments, and very deeply emarginated behind ; last segment scarcely more than half as long as the penulti- mate one. Caudal segment longer than it is broad at the base, and gradually tapering behind, tip obtusely pointed. Superior antenna? scarcely reaching to the middle of the penultimate peduncular joint of the inferior ones, basal joint nearly smooth, flagellum composed in female of 6, in male of about 12 articulations. Inferior antenna? fully twice as long as the body and very slender, the 2 outer joints of the peduncle scarcely spinous, flagellum about the length of the peduncle. 1st pair of legs rather slender, with the carpal and propodal joints of about equal length; 2nd pair with the propodal joint almost as long as the carpal one; the 2 succeeding pairs exceeding the body in length. Natatory legs of the structure characteristic of the genus. Uropoda with the proximal joint oblong oval in form, and edged with about 14 plumose setse, distal joint scarcely half as long, cylind- ric, clothed with very delicate bristles. Colour whitish, semipellucid. Length of adult female about 3 mm. Remarks. The present species, being the first recorded, ought to be re- garded as the type of the genus. It may be easily distinguished from the other 2 species by the smoothness of the cephalon and the anterior segments of the mesosome. It is also of far inferior size, and is less robust of form. Occurrence. I first detected this form in the inner part of the Christiania Fjord, at depths ranging from 30 to 50 fathoms, and have also subsequently found it in several other places on the Norwegian coast, as far north as Tjoto, on the Nordland coast. Its natatory movements are extremely rapid, and are effected by abrupt jerks backwards. When slowly creeping upon the bottom, it somewhat recalls a spider, by its slender, laterally-extended legs, and the deep median constriction of the body. Distribution. Skagerak (Meinert). 137 2. Ilyarachna hirticeps, G. 0. Sars. (PI. LX.) ll//arachna hirticeps, G. O. Sars, Nye Dybvandscrustaceer fra Lofoten. Chr. Vid. Selsk. Porhdl. 1869, p. 167. Specific Characters. Body of a similar appearance to that in the type species, but more than twice as large, and somewhat more robust. Cephalon very broad, with the dorsal face strongly vaulted, and densely clothed with short stout bristles. Anterior edge of the first 4 segments of mesosome very distinctly elevated, and minutely crenulated throughout; lateral paits of 1st segment imper- fectly developed. The 3 posterior segments of mesosome combined about the length of the preceding part of the body ; the anterior segment evenly emarginated behind. Caudal segment of a similar form to that in J. longicornis. Superior antennae comparatively short, not nearly reaching to the middle of the penultimate peduncular joint of the inferior ones, basal joint armed along the inner edge with scattered denticles, flagellum, in female, not attaining the length of the last 2 peduncular joints combined. Inferior antennae scarcely twice as long as the body, penultimate joint of the peduncle armed inside with 7 strong spines. Legs, on the whole, resembling in structure those in the type species, though the 3rd and 4th pairs are somewhat less elongated, and the natatory legs more densely fringed with seta?. Uropoda with the proximal joint rather large, and somewhat widening distally, marginal seta? about 20 in number, distal joint very narrow, linear. Colour whitish grey. Length of adult female 772 mm. Eemarks. This species is nearly allied to the preceding one, but of very much larger size, and, moreover, easily distinguishable by the dense setous clothing of the dorsal face of the cephalon, and by the strongly elevated and finely cre- nulated anterior edges of the anterior segments. Several other minor differences may also be shown to exist, on a closer comparison of the several appendages in the two species. Occurrence. This species would seem to be a true arctic form, having not, as yet, been found south of the Lofoten Islands, whereas it is not unfrequently met with on the Finmark coast as far as Vadso. Distribution. Several stations of the Norwegian North Atlantic Expedition (the present author), Greenland (Hansen). 18 Crustacea. 138 3. Ilyarachna denticulata, G. 0. Sars, n. sp. (PL LXI, fig. 1.) m Specific Characters. Very like the preceding species, both in size and ge- neral appearance, but differing conspicuously in the armature of the body. Ce- phalon of a similar shape to that in /. hirticeps, dorsal face densely clothed with short spines. First segment of mesosome considerably smaller than the 3 suc- ceeding ones, and with the lateral parts imperfectly developed; anterior edge of all 4 segments divided into a regular series of from 10 to 15 very conspicuous dentiform projections. The 3 posterior segments of mesosome smooth, and of a similar appearance to that in I. hirticeps. Caudal segment likewise scarcely differing in shape from that in the said species. Superior antennae rather short, with the lusal joint strongly denticulate inside, and the 2nd joint tipped with several diverg- ing spines, flagellum 8-articulate. Inferior antenna? about twice as long as the body, and rather slender, penultimate joint of the peduncle without any spines inside. Legs and uropoda nearly exactly as in /. hirticeps. Colour whitish. Length of adult female 7 mm. Remarks. This form is so very like I. hirticeps both in size and general appearance, as to be easily confounded with it. On a closer examination, how- ever, it is distinguished pretty well by the peculiar armature of the fore- body. The soft bristles clothing the dorsal face of the cephalon in the above- named species, are here replaced by rigid spines, and the anterior edges of the 4 first segments of the mesosome are not, as in that species, finely crenulated, but divided into coarse spiniform projections. On the other hand, there is no trace of the strong spines occurring in 1. hirticeps on the penultimate peduncular joint of the inferior antennoo. In most other respects there is a very close resem- bhmce between this species and I. hirticeps. Occurrence. L have found this species in several places on the west coast of Norway, from Stavanger up to the Trondhjem Fjord, in depths ranging from 100 to 400 fathoms. Off the Lofoten Islands and the Finmark coast, this species ilocs not seem to occur, and it thus appears to be a more southern form. I had previously confounded this species with 1. hirticeps. 139 Gen. 3. EehmOZOne, G. 0. Sars, n. Syn: Ih/amclnia, G. 0. Sars (pnvt). Generic Characters. Body somewhat resembling in shape that in the genus Ilyarachna, but comparatively shorter and thicker, with the anterior segments of mesosome strongly spinous, the 3 posterior segments short and broad. Caudal segment distinctly notched on each side, at some distance from the tip. Antennae about as in Ilyarachna. Mandibles very large and without a trace of palps. Ambulatory legs resembling those in the genus Ilyarachna; natatory legs, on the other hand, far less fully developed, with the outer joints but slightly expanded. Uropoda with 2 distinct rami issuing from the outer side of the large, lamellar basal part. Remarks, This new genus is founded upon the form previously described by the present author as Ilyarachna coronata. On a closer anatomical examin- ation of this form, I have found it to differ in some particulars rather markedly from the 3 above-described species, so that it ought more properly to be regarded as the type of a nearly-allied genus. Among these differences may be named the absolute absence of mandibular palps, and the biramous character of the uropoda. The genus comprises as yet but a single species. Echinozone coronata, G. 0. Sars. (PI. LXI, fig. 2.) Ilyarachna coronata, G. O. Sars, Nye Dybvamlscrus l aceer fra Lofuten. Clir. Vid. Selsk. Forlidl. 1869, p. 168. Specific Characters. Body very short and compact, scarcely more than twice as long as it is broad. Cephalon with the dorsal face strongly vaulted and perfectly smooth, lateral parts obliquely expanded. Anterior edge of the first 4 segments of mesosome considerably raised, and divided into 6 8 coarse spiniform projections, between which are as many very small denticles, lateral parts of 1st segment simple, those of the 3 succeeding segments each produced into 2 acute lappets. The 3 posterior segments of mesosome comparatively short, and, com- bined, not nearly attaining the length of the anterior division, dorsal face some- what uneven, anterior edge of 1st segment slightly denticulated. Caudal segment scarcely longer than it is broad at the base, lateral edges minutely setous, and exhibiting, at some distance from the tip, a very distinct notch denned in front by a dentiform projection, tip acutely produced. Superior antenna? not reaching to the middle of the antepenultimate peduncular joint of the inferior ones, basal joint of moderate size and without any denticles, nagellum 10-articulate. Inferior 140 antennae not quite twice as long as the body, flagellum nearly attaining the length of the peduncle. 1st pair of legs comparatively short, with the 2 outer joints of about equal length; 2nd pair densely spinous, with the propodal joint longer than the carpal one. The 2 succeeding pairs of legs scarcely as long as the body. Natatory legs less strongly developed than in Ilyarachna, carpal joint of the 2 anterior pairs narrow cordiform, and scarcely longer than the propodal joint, dac- tylus rather elongated. Uropoda with the basal part oblong oval, slightly narrowed distally, and carrying about 12 plumose seta?, outer ramus much smaller than the inner, but well defined. Colour greyish white. Length of adult female 5 mm. Remarks. This species may be easily recognized from the allied forms by its short and compact body, and by the very conspicuous spinous whorls encircling the anterior segments of the mesosome. Occurrence. Besides off the Lofoten Islands, where the species was first discovered, I have met with it occasionally at VadsO, as also in several localities on the west coast of Norway (Espevser, Floro, Aalesund, Trondhjem Fjord), the depth ranging from 100 to 300 fathoms. Out of Norway, it has not yet been recorded. Gen. 4. Aspidaraehna, G. o. Sars, n. Syn: Ilyarachna, G. O. Sars (part). Generic Characters. Body short and compact, with the 2 divisions of mesosome very sharply defined, the posterior one being very large, clypeiform, partly projecting in front over the anterior. Cephalon broad, transverse, evenly convex above, frontal margin slightly emarginated. Caudal segment triangular, rather broad at the base. Superior antenme much more fully developed in male than in female. Inferior antennae of moderate size. Mandibles very strong, cutting edge undivided, molar expansion very small, conic, tipped with slender bristles, palp distinct, though rather feeble. The 4 anterior pairs of legs constructed, on the whole, in a similar manner to that in the 2 preceding genera, though the 3rd and 4th pairs are not particularly elongated. Natatory legs very fully developed. Uropoda with 2 dis- tinct rami, as in the genus Echinozonc. Remarks. This genus also is founded upon a species previously referred by the present author to the genus Ilyarachna. A closer anatomical examination has also in this instance revealed some peculiar features of apparently generic value. Thus, the uropoda, as in the genus Echinozone, are distinctly biramous; 141 but, unlike what is the case in that genus, the mandibles are provided with dis- tinct, though rather small palps. The peculiar fornicate character of the posterior division of the body has given rise both to the generic and specific names. Aspidarachna clypeata 1 ), G. 0. Sars. (PI. LXII.) Ilyaraclma clypeata, G. 0. Sars, Nye Dybvandscrustaceer fra Lofoten. Chr. Vid. Selsk. Forlxll. 1869, p. 168. tfjx'cific Characters. Body scarcely more than twice as long as it is broad, and generally much curved. Cephalon very broad in proportion to its length, frontal edge evenly concaved, lateral parts obliquely expanded. The first 4 segments of meso- some short and distinctly excavated transversally, with the anterior edge considerably elevated and perfectly smooth, lateral parts acutely produced. The 3 posterior seg- ments of rnesosome very large and evenly convex above, forming together a shield-like plate advancing in front over the adjoining part of the anterior division. Caudal seg- ment triangular, scarcely as long as it is broad at the base, tip obtusely pointed. Superior antenna; with the basal joint very large, inner corner considerably pro- duced, and armed with 2 long spines ; nagellum in female short, 3-articulate, in male very much elongated, and divided into numerous short articulations clothed with delicate sensory filaments. Inferior antennae nearly twice as long as the body, the 2 outer joints of the peduncle armed inside with slender spines, fla- gellum about the length of the peduncle. The 4 anterior pairs of legs scarcely different in their structure from those in the 2 preceding genera, except that the 3rd and 4th pairs are very much shorter, not nearly attaining the length of the body, and having the ischial joint the longest. Carpal joint of the 2 anterior pairs of natatory legs strongly expanded, broadly cordiform in outline, and densely fringed with plumose seta?, propodal joint much shorter and oblong fusiform. Last pair of legs, as in the 2 preceding genera, much more slender than the 2 preceding ones. Uropoda with the basal part oblong oval and densely fringed with plumose setae, outer ranius very small, though well defined. Colour whitish. Length of adult female 4 mm. Remarks. This is the only as yet known species of the genus, and may easily be recognized by the short and compact body, and the peculiar fornicate character of the posterior segments of the mesosonie. ') The generic name Aspidonotus given in the plate has been changed in the above manner, because that name has been previously used in Zoology. 142 Occurrence. I first discovered this form off the Lofoten Islands, in depths ranging from 120 to 250 fathoms, and have subsequently found it in 2 other localities of the Finmark coast, viz., Hasvig and Vadso. South of the Lofoten Island, I have not yet met with it, and it would therefore seem to he a northern form. Its swimming motions are exceedingly rapid, and, as in the allied forms, are effected by abrupt bounds backwards. Out of Norway, it has not yet been recorded. Gen. 5. Pseildarachna, G. 0. Sars, n. Syn: llyaraclma, G. O. Sars (part). Generic Characters. Body clavate in form, with the anterior division con- siderably broader, and scarcely shorter than the posterior, being defined from it by a deep constriction. Cephalon large and broad, obtusely truncated in front. The 4 anterior segments of mesosome scarcely excavated transversally, 2nd seg- ment much the largest; the 3 posterior segments but slightly expanded. Caudal segment comparatively large, oblong triangular. Superior antennae very small, and placed far apart, basal joint lamellarly expanded on the outer side, nagellum poorly developed. Inferior antennae strongly built, with the flagellum longer than the peduncle. Mandibles very large, with blunt, undivided cutting edge, molar expansion extremely minute, dentiform, palp absent. Maxilhe and maxillipeds about as in the preceding genera. 1st pair of legs very slender, nearly filiform; 2nd pair, on the other hand, rather strongly built, and considerably longer than the 2 succeeding pairs. Natatory legs rather poorly developed, 1st pair the largest, last pair extremely slender. Uropoda lamellar, with a single very small, nodiforui ramus. Remarks. The present new genus is established to include the very anomalous form previously described by the present author as Ilyarachna hirsiita. The differences which this form exhibits from the other Munnopsidce, are so numerous, and of such an essential nature, that it can hardly be included in any of the above-described genera, but must take its place in a separate genus. The structure of the legs in particular is rather peculiar, and that of the mandibles is also pronouncedly different from that found in the preceding genera. 143 Pseudarachna hirsuta, G. 0. Sars. (PI. LXIII.) Ilyaraclma Idrsuta, G. 0. Sars, Om en anomal Gruppe af Isopoder. Chr. Vid. Selsk. Forhamll. 1863, p. 9. Specific Characters. Body more than twice as long as it is broad, with the greatest width across the 2nd segment of mesosome, surface everywhere clothed with stiff bristles. Cephalon very broad and highly convex above, front obtusely rounded, lateral parts obliquely expanded. Each of the 4 anterior segments of mesosome armed dorsally with 2 juxtaposed denticles, and laterally with an up- turned spine. The 3 posterior segments of mesosome combined scarcely exceeding half the length of the anterior division, the anterior segment the largest, and but slightly emarginated behind ; last segment rather small. Caudal segment some- what longer than it is broad at the base, tip obtusely pointed. Superior antennas with the basal joint produced outside to a linguiform lamellar expansion carrying at the tip 2 auditory seta?; flagellum scarcely longer than the 2nd peduncular joint, and composed of only 3 articulations. Inferior antenna? about one and a half times as long as the body, the 2 outer joints of the peduncle rather strongly built, and clothed with scattered spiniform bristles, flagellum very slender and composed of 14 narrow and elongated articulations. 1st pair of legs extremely slender, with the propodos long and narrow; 2nd pair very robust, with the ischial joint much expanded distally, and clothed inside with strong seta?.. The 2 succeeding pairs shorter and much narrower than the 2nd pair, with the dactylar joint not unguiform, tipped with diverging bristles. 1st pair of natatory legs considerably larger than the other 2, though having the outer joints but slightly expanded and fringed with a very restricted number of ciliated seta?; last pair extremely slender, with the propodal joint very narrow, linear. Uropoda with the basal joint rather large, oblong oval, and edged with numerous short plumose seta?, terminal joint extremely minute, nodiform. Colour whitish grey. Length of adult female 2 1 /-2 mm. Remarks. This form was described by the present author as early as in the year 1863, and at that time referred to the genus Ilyarachna. It is easily recognizable by the densely hirsute body and the peculiar structure of the legs. More frequently, however, it is so closely obtected with muddy particles adhering to the stiff bristles, that its true form is rather difficult to observe. Occurrence. The only place where I have hitherto met with this peculiar form, is in the innermost part of the Christiania Fjord, where a few specimens were taken from a depth of about 30 fathoms, muddy bottom. Out of Norway, it has not yet been recorded. 144 Gen. 6. EliryCOpe, G. 0. Sars, 1863. Generic Characters. Body rather compact and distinctly depressed, more or less oval in outline, with the 2 divisions of mesosome less sharply marked off from each other than in the preceding genera. Cephalon of moderate size, deeply emarg- inated on each side for the insertion of the antenna?, frontal part more or less projecting. The 4 anterior segments of mesosome comparatively, short, subequal, transversely excavated dorsally; the 3 posterior segments very large and broad, with the dorsal face smooth and convex. Caudal segment semi-oval, obtusely rounded at the tip. Superior antennae with the basal joint large and massive, flagellum multiarticulate. Inferior antennae very slender and elongated. Mandibles normally developed, with the cutting edge divided into strong teeth, and the molar expansion rather thick, palp comparatively large, with the terminal joint lamellar and much curved. Maxillae normal. Maxillipeds pronouncedly lamellar, penulti- mate joint of the palp produced at the end inside to a digitiform lappet, epignath large, and of different form in the different species. 1st pair of legs slender, but shorter than the 3 succeeding pairs, which are subequal and generally very much elongated, terminating in a slender claw. Natatory legs very fully developed and all of same structure, carpal and propodal joints strongly expanded, foliaceous, and densely edged with plumose setae, dactylus distinct. Uropoda comparatively small, biramous, basal part net lamellarly expanded, rami linear. Remark*. This genus, established by the present author in the year 1863, is perhaps the most typical of the Munnopsidae, in so far as the natatory legs- are more powerfully developed than in any of the other genera. The swim- ming motion of the animal is accordingly extremely rapid and of longer duration than in the other Munnopsidce. The genus is chiefly characterised by the de- pressed oval body, the broad caudal segment, the uniform structure both of the ambulatory and natatory legs, and finally, by the structure of the uropoda. Rather a large number of species have been described in recent times, from differ- ent parts of the Oceans, amounting to 22 in all. From the Challenger Expedi- tion alone, no less than 13 species have been recorded by Mr. Fr. Beddard; but some of these ought perhaps more properly to be separated as types of nearly- allied genera. To the fauna of Norway belong 8 species, to be described below. Munnfdae . I s op o da- i. 49. G.O. S ars, autogr . Pleurotion spinosum , G .0. Sars. Desmosomidae, I s op o da.. PI. 50. . ^ G.O. S ars, autogr . Nannoniscus oblongus, G.O.Sars. Desmosomidae. 1 S O 3 O CLQ__ P1.53. G.O. S srs, autogr. Desmosoma lineare, G.O.Sars. Desmosomidae . 1 s op o da. PI. 54. G. 0. S ars, autogr . !. Desmosoma lineare, G.O.Sars.$. 2. armatum.G.O.Sars. Munnopsidae. I s op o da.. PI. 57. G.O. S srs, autoqr . Munnopsis typica, M. Sars. Munnopsidae. I s op o da- . 58. G.O. S ars, autogr , Munnopsis typica, M. Sars. ( contin.) Munnopsida. I s op o da- i. 59. G.O. S ars, autocjr . Jlyarachna loncjicornis, G.O.Sars. Munnopsidas. I s op o cia__ PI. 60. 6. 0. S ars, autogr . Jljarachna hirticeps, G. 0. Sars. IVlunnopsidse. I s op o da. PI. 6! 1. Jlyarachna denticulata, G.O.Sars. 2. Echinozone coronata, G.O.Sars. - IVlunnopsidae. I s op o da. PI. 62. G.O. S ars, autogr . Aspidonotus clypeatus, G. 0. Sars. ' Munnopsidae. I s opo da. PI. 63. =&&' G.O. S ars, aulogr. Pseudarachna hirsuta, G. O. Sars. Munnopsidae. I s op o da. PL 64. G 0. S srs, autogr . Eurycope cornuta, G. 0. Sars. 145 1. Euryeope eornuta, G. 0. Sars. (PI. LXIV.) Ewycope eornuta, G. 0. Sars, Om en anomal Gruppe at' Isopoder. Chv. Vid. Selsk Fovhandl. 1863, pag. 5. 83-11 : Euryeope robusta, Harger. Specific Characters. Body oblong oval in outline, being more than twice as long as it is broad, and with the anterior division not attaining half the length of the posterior. Cephalon with the lateral corners pointed, front produced to an acute, rostriform projection, which, however, does not extend to the end of the basal joint of the superior antenna?. The 4 anterior segments of rnesosome comparatively short, and produced on each side to acute, anteriorly-pointed lappets. The 3 posterior segments of mesosome of nearly equal size, and distinctly denned, antero -lateral corners acutely produced. Caudal segment very large, nearly as long as the 2 preceding segments combined, semi-oval in form, edges evenly curved and perfectly smooth, antero-lateral corners projecting. Superior antennae in male fully half the length of the body, in female somewhat shorter, flagellum very slender and flexible, being composed of 20 in female, in male of about 50 articulations carrying delicate sensory filaments. Inferior antenna? more than 3 times as long as the body, penultimate joint of the peduncle clothed everywhere with adpressed spines, some of which, attached to the inner edge and tip, are stronger than the others. Epignath of maxillipeds securiform, outer edge an- gularly produced. 1st pair of legs with the propodos much shorter than the carpus, both simple, linear, and clothed with short bristles, dactylus very small; the succeeding pairs very slender, somewhat exceeding the body in length. Nata- tory legs with the carpal joint cordiform, propodal one of about the same length, but somewhat narrower, oblong oval, dactylus scarcely exceeding half the length of the former. Female operculum subpentagonal in form, and distinctly carinated along the middle; male operculum transformed in the usual manner. Uropoda with the rami subequal in length, the outer one narrower than the inner. Colour of the whole dorsal face, light reddish brown. Length of adult male 4 mm. Remarks. This is much the largest and finest of the Norwegian species, and may be regarded as the type of the genus. It is, however, considerably sur- passed by some of the exotic species, especially the huge arctic form E. giyantea G. 0. Sars, which reaches to a length of 34 mm. The E. robusta of Harger is unquestionably identical with the present species. Occurrence. This species occurs along the whole coast of Norway, from the Christiania Fjord to Vadso, in depths ranging from 50 to 400 fathoms. In some places, for instance in the Hardanger Fjord and Trondhjem Fjord, I have 19 Crustacea. 146 taken it very plentifully on a muddy bottom ; but as the appendages are extremely brittle, it is rarely secured in a perfect condition. Difttrihtiti'jn. Several Stations of the Norwegian North Atlantic Expedition (the present author). Skagerak (Meinert). Atlantic coast of North America (Harger). 2. Eurycope producta, G. 0. Sars. (PI. LXV.) Eurycope producta, G. 0. Sars, Beretning om en i Sommeren 1865 foretagen Reise ved Kysterne af Christianias og Christiansands Stifter. pag. 32. Sepcific Characters. Body oval, about twice as long as it is broad, and slightly tapering both in front and behind. Cephalon with the frontal part con- siderably produced, forming a narrow linguiform projection slightly bilobed at the tip, outer edges of the lobes minutely denticulate. Anterior segments of mesosome distinctly excavated above, lateral parts acutely produced in front; the 3 posterior segments all well defined and of about equal length, antero-lateral corners pro- duced. Caudal segment rather large, nearly twice as broad as it is long, and evenly rounded at the tip, edges perfectly smooth. Superior antennae rather elongated, with the flagellum composed of about 20 articulations. Inferior antennae about 3 times as long as the body, penultimate joint of the peduncle edged inside with slender spines, flagellum about the length of the peduncle. Epignath of maxilli- peds slightly angular outside. 1st pair of legs slender, with the propodal joint scarcely more than half as long as the carpal one; the 3 succeeding pairs some- what exceeding the length of the body, and very slender; 2nd pair comparatively stronger in male than in female, with the carpal joint slightly dilated and spinous inside. Natatory legs of a similar structure to that in E. cornuta, though having the dactylus comparatively smaller. Uropoda with the outer ramus much narrower, but scarcely shorter than the inner. Colour of dorsal face light yellow, all the segments bordered behind with light chestnut. Length of adult female 3 mm. Remarks. This species is nearly allied to E. cornuta, but of smaller size, and is moreover easily distinguished by the less oblong body, the greatly produced frontal part, and the different colouring of the dorsal face. Occurrence. I have met with this species not rarely in several local- ities of the Norwegian coast, from the Christiania Fjord to Vadso, in depths ranging from 60 to 400 fathoms. Out of Norway it has not yet been recorded. 147 3. Eurycope phallangium, G. 0. Sars. (PI. LXVI.) Eurycope phallangium, G. 0. Sars Oni en am>nml Grnppe af Isopoder (Christiania Vid. Selsk. Forh. 1863), p. 6. Specific Characters. Body broadly oval, not nearly twice as long as it is broad, greatest width in the middle. Cephalon with the frontal part conically produced. Fifth and 6th segments of mesosome continent in the middle, forming together a large vaulted plate, deeply emarginated behind. Caud;il segment com- paratively small, subpentagonal in form, tip obtusely rounded, lateral edges fringed with stiff bristles. Superior antennae not much elongated, flagellum composed of about 10 articulation. Inferior antennae exceedingly slender and elongated, 4 to 5 times as long as the body, the 2 outer joints of the peduncle very narrow and but sparsely setiferous, flagellum longer than the peduncle. Molar expansion of the mandibles rather narrow, attenuated distally. Epignath of maxillipeds lanceolate, without any angle outside. 1st pair of legs comparatively short and rather strongly built, propodal joint fully as long as the carpal one, the latter slightly dilated and curved, with a setiferous ridge inside. The 3 succeeding pairs of legs extremely slender and elongated, more than twice as long as the body, and having the ischial joint produced to an unusual degree. Natatory legs with the carpal joint rather large, obcordate, propodal joint much smaller and narrow oblong in form, dactylus very much produced, considerably exceeding the propodal joint in length, and distinctly biarticulate, proximal joint lanceolate, distal one spiniform. Uropoda with the outer ramus a little longer, but much narrower than the inner. Colour of dorsal face light yellowish grey, with a slight reddish tinge. Length of adult female scarcely exceeding 2 mm. Remarks. In several respects this species differs rather markedly from the 2 preceding ones, whereas it exhibits a close relationship to some of the suc- ceeding species. It is therefore most probable that it will be found advisable to establish for these species a separate genus. The specific name refers to the ex- cessively elongated inferior antennae and ambulatory legs. Occurrence. This species is very common along our whole south and west coasts, and extends northwards to Hasvig in Finmark. It occurs in depths ranging from 50 to 300 fathoms, on a bottom consisting of muddy clay. In spite of its small size and inconspicuous colouring, the animal may be easily detected on placing a portion of the mud taken up by the dredge in a shallow vessel, when, like several other small Crustacea, it will Ho at up to the surface, without being able to immerge itself again. As, however, the several appendages of the body are extremely fragile, it is rather a rare occurrence to get a specimen with all of them uninjured. Though there cannot be any doubt that this form 148 must also occur off the coasts of other countries, it has not yet been recorded out of Norway. 4. Eurycope latirostris, G. 0. Sars. (PI. LXVII, fig. 1.) Eurycope latirostris, G. O. Sars. Oversigt of Norges Crustaceer, I. p. H7, PI. 2. fig. 6. Specific Characters. Very like E. phallangium as to its external appear- ance. Frontal part of cephalon, however, very different, forming a broad lingui- form plate slightly emarginated at the tip, and minutely denticulated outside. Fifth and 6th segments of inesosome, as in E. phallangium, confluent in the middle. Caudal segment comparatively larger than in that species, but of a similar shape and armament. Inferior antennae scarcely more than twice the length of the body, with the flagellum much longer than the peduncle. Ambula- tory legs of a similar structure to those in E. phallangium, though not nearly so much elongated. Natatory legs with the dactylus scarcely attaining the length of the propodal joint. Uropoda with the outer ramus shorter and narrower than the inner. Colour about as in E. phallangium. Jjength of adult female 2 mm. Remarks. This species is very nearly allied to E. phallangium, and may indeed easily be confounded with it. On a closer examination, however, some well-marked differences are to be found, showing it to be in reality a well- defined species. Thus the frontal part exhibits a totally different appearance, being rather broad, linguiform, and slightly emarginated at the tip. whereas in E. phallangium this part tapers to a point. Moreover the inferior antennae and the ambulatory legs are less elongated, though of a similar slender form to those in E. phallangium; finally, the dactylus of the natatory legs is much shorter, and the rami of the uropoda are shorter and thicker. Occurrence. Only a few specimens of this form have hitherto come under my notice. That first described was found in the outer part of the Hardanger Fjord. Some other specimens were subsequently detected on looking over a great number of E. phallaug turn taken in the inner part of the Stavanger Fjord from a depth of 150 to 200 fathoms. 5. Eurycope furcata, G. O. Sars. (PI. LXVII, fig. 2.) Knrii<'(>in_: furcata, G. 0. Sars, Nye Dybvandscrustaceer fra Lofoten. Chr. Vid. Selsk. Fork. 1869, p. Itio. *l>rcific Chann-tcr*. Body oval, greatest width exceeding half the length, and occurring somewhat behind the middle. Frontal part of cephalon greatly produced, forming a narrow, conical plate, minutely bifurcate at the tip, and ex- 149 tending MS \\\r as the 3rd peduncular joint of the inferior anteniue. Anterior segments of mesosome short, and transversely excavated, with the lateral parts acutely produced in front. Fifth and 6th segments confluent dorsally, and forming a large vaulted plate deeply emarginated behind. Caudal segment semioval, edges evenly curved and perfectly smooth. Inferior anteniue not very elongated, scarcely exceeding by more than V 4 of their length that of the body, the 2 outer joints of the peduncle edged with slender spines, flagelluw much shorter than the peduncle. Epignath of maxillepeds oblong lanceolate, coarsely striolate. 1st pair of legs but little different from the 3 succeeding ones, which are rather short, scarcely exceeding half the length of the body. Natatory legs with the propodal joint rather broad, oval, constricted at the base, dactylus narrow lanceolate, and about half the length of the former joint; last pair considerably smaller than the 2 pre- ceding ones, and having the carpal joint lamellar!} 7 expanded outside. Lropoda with the outer ramus much shorter and narrower than the inner. Colour whitish, semipellueid. Length of adult female scarcely attaining 2 mm. tienxn'k*. In the coalesced 5th and 6th segments of the mesosome, this species agrees with the 2 preceding ones, but otherwise it is rather different, and easily recognisable by the conically produced, and minutely bifurcate frontal part, the unusually short inferior antennae and ambulatory legs, and the whitish colour. Occurrence. I first detected this form off the Lofoten islands, at Skraa- ven. where it is not uncommon in 100 120 fathoms, on a bottom consisting of sandy clay. Subsequently I have also met with it in a widely distant locality, viz.. iu the inner part of the Stavanger Fjord, at Jelso. Out of Norway this form has not yet been recorded. 6. Eurycope mutica, G. 0. Sars. (PL LXVIIJ, %. 1.) Eurycope mutica, G. 0. Sars. Om en anomal Gruppe af Isopoder. Clir. Vicl. Selsk. Fork. 18H3. p. <>. Specific Characters. Body broadly oval, greatest width exceeding half the length and occurring in the middle. Frontal part of cephalon rather broad and obtusely rounded at the tip. Anterior segments of mesosome with the lateral parts not acutely produced in front; 5th and 6th segments imperfectly defined dorsally. Caudal segment not very large, slightly coarctated towards the tip. which is narrowly rounded, lateral edges setiferous. Superior antenna? compara- tively small, flagellum composed of only 5 or 6 articulations. Inferior antenna? very slender, fully twice as long as the body, flagellum more than twice the length of the peduncle. Epignath of inaxillipeds short and broad, obtusely trun- cated at the tip. 1st pair of legs with the propodal joint much shorter than 150 the carpal one. dactylus minute; the 3 succeeding pairs rather slender, though scarcely exceeding the body in length, dactylus very long and slender; 2nd pair somewhat more strongly built in male than in female, with the carpal joint slightly dilated. Natatory legs with the propodal joint broadly oval, much constricted at the base, dactylus narrow, styliform. Uropoda extremely small, outer ramus scaively half as large as the inner. Colour of dorsal face very dark fuscous, towards the edges of the segments almost black. Length of adult female 1 1 /-> mm. Remarks. This species may be easily distinguished from the preceding ones by the broad, obtusely rounded frontal part of the cephalon, and by the very dark colour of the dorsal face. It is also rather inferior in size. Occurrence. I first found this form in the inner part on the Christiania Fjord, and have subsequently met with it in many other places of the Norwegian coast, and as far north as Bodo. It is not strictly a deep-water species, being often found in only a few fathoms' depth among alga?. Its swimming motions are extremely rapid, and are effected by long abrupt bounds backwards. Out of Norway this form has not yet been recorded. 7. Eurycope pygmaea, G. 0. Sars. (PI. LXVIIT, fig. 2.) Eurycope p;/ articulations. Legs comparatively shorter than in the type species, but otherwise of a similar structure. Inner ramus of 1st pair of pleopoda in male greatly produced, with the terminal joint narrow knife-shaped; that of 2nd pair Inarticulate, proximal joint very short, distal joint long and slender, styliform. Uropoda rather -hort. with the rami nearly equal, and but little longer than the 163 basal part. Colour of dorsal face whitish, semipellucid, with a few light brown pigmentary ramifications across the segments, and a double row of irregularly lobular, opaque white patches along the middle of the back, probably caused by some internal matter (renal excretions). Length of adult female scarcely ex- ceeding 2 mm. 'ks. I have not been enabled to identify this form with any of the earlier described species. At first I thought that it might perhaps be the form mentioned by Dr. M. Weber as T. [>tt*-iUtis r/ir. l/ith/rn: but there are several things which forbid such an identification. For instance. Dr. Weber says that the dorsal face in his form is perfectly smooth and of a similar dark brown colour to that in the type species, and the flagelhim of the antennae is stated to be 4-articulate, not, as in the present species, 3-articulate. Occurrence. I have only met with this form in a single locality in the immediate vicinity of Christiania. but there rather abundantly. It occurred on an open plain, close to the railway, beneath stones and pieces of wood, in company with Trichoniscoidcs albidus, to be described below. It is far less agile than T. pusillus, through not nearly so slow in its motions as the just-named form. 3. Triehoniscus roseus (Koch). (PL LXXIII, fig. 1.) llai rofsea, Koch, Deutschlands Crust, p. 2^. fig. llj. Syn: Philougria rosea, Kinalmn. ^l>ccific Characters. Body oblong oval, greatest width almost attaining half the length, dorsal face but slightly convex, and rough, owing to numerous densely crowded tubercles arranged in transversal rows. Cephalon transversely oval, with the lateral lobes well-marked, denticulate, front nearly straight. Lateral parts of mesosome more expanded than in the other species. 1st pair rather broad and partly flanking the cephalon, the 3 posterior pairs recurved and acuminate. Me- tasome (in male) exceeding half the length of the mesosome, and but little more than half as broad ; terminal expansion of last segment transversely truncate, with 4 small apical spinules. Antemmhe with the last joint much longer than the 2nd, and carrying 6 sensory filaments, 5 apical and 1 lateral. Antenna? comparatively slender, attaining l / ?J of the length of the body, flagellum composed of 4 articulations. Last pair of legs in male peculiarly modified, having the meral joint strongly dilated, and produced inside to a large conical prominence, in against which the succeeding joint admits of being bent. Inner ramus of 1st pair of pleopoda in male, with the terminal joint dilated at the end in the form of n little bowl of a spoon; that of 2nd pair rather strong and distinctly 3-ar- ticulate, terminal joint knife-shaped and denticulate inside. Uropoda with the outer ramus about twice the length of the basal part, inner ramus somewhat narrower, but scarcely shorter. Colour of dorsal face in life of a clear minium- rose. Length of adult male 5 mm. L'cmnrJcs. This species, first described by Koch, is easily distinguished by its comparatively broad and flattened body, the dorsal face of which is densely granular, and by its beautiful colour, which, ho \vever, is only seen in fresh specimens. The structure, in the male, of the last pair of legs, and of the inner ramus of the 2 anterior pairs of pleopoda is rather peculiar, and has been well described by Dr. M. Weber. Occurrenct 1 . The occurrence of this species in Norway has, it is true, not yet been demonstrated; but. as it is not uncommonly found in Denmark, I am much disposed to believe, that, on a closer investigation, it will also prove to belong to the fauna of Norway. The figures here given are from specimens kindly sent to me from the Museum of Copenhagen. According to Mr. Budde-Lund. it is chiefly found in garden hot-houses. Distribution. Denmark, Germany, Holland, Britain, France, Spain, Italy, Dalmatia, Algeria. Gen. -i. Triehoniseoides, G. o. s a rs, n. Generic Cluir<-t<'dfic Characters. Body oblong oval, with the sides almost parallel, dorsal face slightly convex, and obtusely granular in the middle of the segments. Cephalon almost wholly flanked by the side-plates of the 1st segment of meso- some, lateral lobes rather large, and narrowly rounded at the tip, frontal lobe very prominent and evenly curved, almost semicircular. Side-plates of mesosome 183 rather large, sub-discontiguous, 1st pair securiform in shape, posterior corners of this and the succeeding pairs acuminate. Metasome scarcely occupying y 4 of the length of the body, epimeral plates of 3rd to 5th segments prominent, recurved; last segment nearly as long as it is broad at the base, outer part conically pro- duced and plane above. Antennae slender, though scarcely attaining half the length of the body, flagellum shorter than the last peduncular joint, and having its proximal articulation scarcely more than half as long as the distal one. Legs about as in P. Rathkei. Opercular plates of all pleopoda provided with air- cavities. Uropoda of moderate size, resembling those in P. Rathkei. Colour of dorsal face more or less dark grey, with a regular row of whitish patches on each side, at the base of the side-plates of mesosome, and an assemblage of less distinct wavy stripes on each side of the median line; edges of the side-plates tinged with light yellow. Length of adult male 11 mm. Remarks. For the identification of this interesting species, not yet found in any of the Scandinavian countries, I am indebted to Mr. Budde-Lund, who kindly sent me for comparison some specimens of this form from the central part of Europe. It is nearest allied to P. Rathkei, but easily distinguishable from it by the very prominent cephalic lobes, of which the middle one (frontal lobe) especially exhibits a rather peculiar appearance from its regular semicircular form. Occurrence. I have hitherto only succeeded in finding 2 specimens of this form, a female and a male. They were taken this summer in the neigh- bourhood of Christiania (Bygd0) beneath loose bark, and were at first confounded with P. Rathkei, to which species it bears a rather close resemblance. Distribution. Central part of Europe: Upper Pfaltz, Bohemia, Saxony. ia, Tyrol. Gen. 5. MetOpOnOFthUS, B.-Lund, 1879. Syn: Porcellionides, Miers. Generic Characters. Body oblong, subdepressed, with very thin integu- ments. Cephalon with the lateral lobes very small, frontal lobe obsolete. Side- plates of mesosome but very slightly prominent. Metasome abruptly contracted, with the epimeral plates of 3rd to 5th segments sub-appressed ; last segment comparatively short, triangular. Eyes well developed, lateral. Antennula? very small, with the last joint quite short. Antennae slender and elongated, flagellum biarticulate. Oral parts nearly exactly as in Porce.llio. Legs slender, and greatly 184 increasing in length posteriorly. Opercular plates of the 2 anterior pairs of pleo- poda with air-cavities, more rarely also those of 3rd or of all pairs. Copulative organs of male nearly as in Porcellio. Uropoda rather produced, and of a similar structure to that in Porcellio. Remarks. This genus established by Mr. Bndde-Lund, is nearly related to Porcellio, though easily distinguishable from it by the smallness of the cephalic lobes, the poor development of the side-plates of the mesosome, and the abruptly contracted metasonie. The generic name refers to the fact, that the frontal edge of the cephalon is nearly straight, not as in Porcellio produced in the middle. Mr. Budde-Lund describes no less than 35 species of this genus, chiefly from the southern part of Europe. Only a single species belongs to the fauna of Norway ; it will be described below. Metoponorthus pruinosus (Brandt). (PI. LXXX, fig. 2.) Porcellio pruinosus, Brandt, Consp. monogr. Crust. Isop. terrestr. p. 19, fig. 21. Syn : Porcellio truncatus, M. Edw. maculicornis, Kocli. frontalis, Lereb. Porcellionides flavo-vittatus, Miers. Specific Characters. Body oblong, more than twice as long as it is broad, dorsal face but slightly convex and nearly smooth, though, on a closer examina- tion, exhibiting a very fine granulation. Cephalon transversely quadrangular, al- most twice as broad as it is long, lateral lobes extremely small, frontal margin straight. Side-plates of the 4 anterior segments of mesosome scarcely at all projecting, those of the 3 posterior segments somewhat larger, with the posterior corners obtusely acuminate. Metasonie not attaining 1 U of the length of the body, and much narrower than the mesosome, epimeral plates of the 2 anterior segments concealed, those of 3rd to 5th segments comparatively small, recurved ; last segment nearly twice as broad at the base as it is long, subtriangular, tip pointed. Antennula? with the last joint scarcely longer than the middle one. Antennae very slender and elongated, exceeding half the length of the body, flagellum somewhat shorter than the last peduncular joint, and having its prox- imal articulation nearly twice as long as the distal one. Legs very slender, minutely spinulose inside, propodal joint narrow, sublinear. Opercular plates of only the 2 anterior pairs of pleopoda provided with air-cavities, and of somewhat different shape in the two sexes. Uropoda with the outer ramus nearly twice as long as the basal part, inner ramus extending scarcely to the middle of the Munnopsidas. I s op o da. PL 65. G.O. S ars, autogr. Eurycope producta, G. 0. Sars. Munnopsidae. I s op o da- i. 66. G.O. S ars, autogr. Eurycope phal lancji u m, G.O.Sars. ._ r _. I S n O CLQ-- PI. 67. G.O. S ars, autogr 1. Eurycope fatirostris, G. 0. Sars. 2. Eurycope furcat^, G.O.Sars. Munnopsidae. I s op o da._ PI. 68. G.O. S ars, autogr . 1. Eurycope mutica, G. 0. Sars. 9. Eurvcnne nv^maea. G.O. Sars. Munnopsidas. I s opo da.. PI. 69. G.O. S ars, autogr . Eurycope megalura, G. 0. Sars, s op o G.O. S ars, autogr . Lig'ia oceanica, (Lin.). I s op o da. PI. 71. / "" v >*'ft\ -' G.O.Sars, autogr. Ligidium hypnorum, ( Cuv.). Trichoniscidae. I s op o da. PI. 72. ,. f L - : 4 ; - 4. , / I f -1 { f '' ^* - AV G.O. S ars, autogr . 1. Trichoniscus pusillus, Brandt. 9 Trirhnn i.gicus nv^>m?eus G.O.SaPS. Trichoniscidse. I s op o da__ PI. 73. ^^*4=i^- '/: , _ Trichoniscus roseus, (Koch). 2. Trichoniscoides albidus, (B-Lund) Trichoniscidae. 1 S O ]3 O CLQ._ PI. 74. f-L t to,* " *. X i ' A G. 0. S ars, autogr . 1. Haplophthalmus Mengii, (Zaddach). 2^ D:o danicus, B-Lund. Oniscidae. I s opo ..,. - . A t ! m , , , , . - - . - < - . G.O. S ars, autogr . 1. Philoscia muscorum, (Scopoli). 2. Platyarthrus Hoffmanseggi, Brandt. Is op o PI. 77 t n . " / . G.O. S ars, autogr 1. Porcellio scaber, Latr. 2. D:o var. marmorata. Oniscidae. I s op o da. PI. 78. . I If r ' eV\ : G. 0. S srs, autogr 1. PorceUio pictus, Brandt. D:o dilatatus, Brandt. Oniscidse. I s op o da- i. 79. 6 r I G.O. S ars, autogr 1. Porcellio Rathkei, Brandt. 2- D:o faevis, Latr. Oniscidae. I s op o da. P! . 80. , ;> &f&. G. 0. S ars, autogr . 1. Porcellio Ratzeburgi, Brandt. 2. Metopo north us pruinosus, Brandt. Oniscidaa. I s op o da- . 81 i . " '\ ' : - . :-\ ' >< -' - ' ' ---:''T^~^ i / i! . .' I ! i ' ftL G.O. S ars, autogr . Cylisticus convexus, (de Geer). Armadillidiidas. I s op o da- i. 82. $ ~psa V., V^,. ' I / ,-; ^\ ^^' ' I si . -.'-' . . T __^_w -^*ju,mm^ "j , , sar r -i _ -- - ;. i\ \ " , /^ ^> ' G.O. S ar's. autogr. 1 n i-ii-i- /i/ i\ Mrmadillidium opacum, (Kochj. 2. Armadillidium pictum, Brandt. .^ A rm a Hillirlium m j Ir.hft I h j m Brandt. JBopyridae. I s opo da- t G.O S ars, autogr 1 n ... / , \ Bopyrus sqvillarum, (Latr.j. 2. Bopyroides hippolytes, (Krayer). Bopyridas. I s op o da. Pl. 85. G.O. S ars, autogr 1. Pseudione affinis, G. 0. Sars. 2. Pseudione Hyndmanni, ( Bate & Westw.). Bopyridae. I s op o da. PI. 86. G.O S ars, autogr. 1. Pseudione crenulata, n. sp. 2. Pleurocrypta longibranchiata ( Bate & Westw.). Bopyridse. I s or) o d.a_ JL PI. 87 uu H G.O. S 0rs, antoqr . Pleurocrypta marginata, n. sp. Pleurocrypta microbranchiata, n. sp. Bopyridae. I s op o da.. PI. 88 G. 0. S ars, autogr Athelges paguri, (Rathke). 185 outer. Colour of dorsal face light reddish brown, the segments of mesosome being bordered behind with darker brown, and having on each side of the median line a group of lighter dots or stripes; antennae banded with white. Length of adult female 9 mm. Remarks. This form has more generally been recorded under the specific name maculicornis proposed by Koch; but, as the name pruiiiosus is the older one, it ought certainly to be retained. Some other synonyms are quoted above. It is easily recognizable by the oblong, flattened body, the abruptly contracted meta- some, and the long and slender antennae, in these points somewhat resembling Philoscia muscorum, from which, however, it is at once distinguished by the bi- articulate antennal flagellum. Occurrence. I have met with this form not infrequently in the immediate vicinity of Christiania, especially in refuse-heaps, together with PorceUio scaber; and it has also been found by conservator Storm in similar situations at Trondhjem. It is a very agile animal, running about with great rapidity when disturbed; and, as the integuments are very thin and soft, it is easily injured when being captured, unless great care be exercised. Distribution. Greater part of Europe, North Africa, North and South America, Sumatra, Madagascar, etc. Gen. 6. CyliStleUS, Schnitzier, 1853. Generic Characters. Body oblong, very convex, capable of being rolled up into a perfect ball, integuments rather hard. Cephalon with the lateral lobes distinct, median lobe very small or obsolete. Side-plates of [mesosome large, those of 1st segment the largest. Metasome not abruptly contracted, epimeral plates of 3rd to 5th segments well developed, recurved ; last segment conically produced behind. Eyes distinct, lateral. Antennulse with the last joint conically produced. Antennae long and slender, with the flagellum biarticulate. Oral parts of a similar structure to that in Porcellio. Legs of moderate size, successively increasing in length behind. Opercular plates of all the pleopoda provided with air-cavities. Copulative appendages of male of a similar structure to that in J'urcrlfio. Uropoda rather much produced, especially in male ; inner ramus very narrow, and issuing far in front of the outer. 21 Crustacea. 186 Remarks. The present genus, established by Mr. Schnitzler, is nearly allied to PorccUio, though in some points, especially in the very convex body and its capability of being rolled up into a nearly perfect ball, it exhibits, as it were, a transition to the next family, the ArmadiUnli'nlir. Mr. B.-Lund describes 7 species of this genus. Of these only a single species is represented in the northern part of Europe. Cylisticus convexus (De Geer). (PI. LXXXI.) (hiiscits cnure.rus, De Geer, Mem. ties Insectes., Vol. VII. p. 553, PL 35, fig-. 11. Syn: Porcellio spinifrons, Brandt. fcem, Koch. armadilloides, Lex-eboullet. Specific Charach'rs. Body oblong oval, more than twice as long as it is broad, side-contours nearly parallel, dorsal face strongly vaulted and perfectly smooth. Oephalon short, transverse, almost 3 times as broad as it is long, lateral lobes rather large, obliquely truncated at the tip. median lobe forming a very small, but distinct acute projection. Side-plates of 1st segment of mesosome very large, partly flanking the cephalon. and acutely produced behind; the succeed- ing pairs with the posterior corner less acute. Metasome not attaining half the length of the mesosome, epimeral plates of the first 2 segments concealed, those of the 3 succeeding segments large, recurved, their lateral margins being continuous with the sides of the mesosome; last segment about as long as it is broad at the base, its terminal part conically pointed, and extending as far as the basal part of the uropoda. Eyes rather large and convex. Antennulse with the last joint about as long as the basal one. and conically pointed. Antennae very slender, considerably exceeding half the length of the body, flagellum a little shorter than the last peduncular joint, and having its 2 articulations subequal in length. Legs moderately slender, and of same structure in the 2 sexes. Inner mini of 1st pair of pleopoda in male with the terminal parts divergent. Uropoda rather large, with the basal part oblong quadrangular, and distinctly keeled along the lower side, outer ramus narrow lanceolate, in male considerably exceeding the basal part in length; inner ramus very narrow, linear, and issuing far in front, thus but slightly projecting beyond the basal part. Colour of dorsal face dark iron grey, with a regular row of light patches along each side of the meso- some, and in each segment a group of less conspicuous flexuous stripes on either side of the median line; uropoda generally ferruginous. Length attaining 12mm. 187 Remarks. This form was described as early as in the year 1778 by De Geer as U-iiiscus convcxus. The Pored I to ar-maa'iUoides of Lereboullet is un- questionably identical with it, and, according to B.-Lund, P. spinifrons of Brandt and P. ItKt-is of Koch ought also to be referred to this species. It is easily recognised from our other Oniscidse by its strongly convex body and its capa- bility of being rolled up into a ball, in which respect it strongly recalls the species of the genus Armadillidium. The slender antennae and the very diffe- rent structure of the uropoda, however, suffice at once to distinguish it from that genus. Occurrence. I have found this form not infrequently in the neighbourhood of Christiania, as also at Drobak and Skien; and some specimens were, moreover, sent to me by Mr. Ellingsen, who collected them near Kragero. It is gene- rally found in rather dry situations, beneath stones, especially where the ground consists of loose pebbles. It moves about rather quickly, but, when alarmed, at once rolls its body up into a ball, which easily escapes the eye of the observer. Distribution. Sweden, Denmark, British Isles, Germany, Bohemia, Hol- land, Belgium, France, Turkey, Caucasus, North America. Fam. 4. Armadillidiidae. Characters. Body convex, contractile into a ball; integuments strongly incrusted. Cephalon flanked by the side-plates oi the 1 st segment of mesosonie, front sub-truncate, marginate, lateral lobes distinct, median lobe obsolete, epistome vertical. Metasome not abruptly contracted, terminal segment short and broad. Antenna 1 , comparatively small, with the tiagellum biartieulate or triarticulate. Oral parts of a similar structure to that in the Oniscidce. Legs comparatively short. Opercular plates of all the pleopoda, or only of the 2 anterior pairs, provided with air-cavities. Copulative appendages about as in the Onixcidce. Uropoda short, not extending beyond the limits of the last segment and the epimeral plates of the penultimate one. The young, on leaving their mother, have all the 7 segments of mesosome distinctly defined. Remarks. The present family agrees in most points rather closely with that of the Oniscidce, and it is somewhat questionable, if it should in reality be kept apart, as there are transitory forms between the two families, e. g. the 188 above-described genus Cylisticus. Yet there are some characters which seem to distinguish all the forms belonging to this family, viz, the peculiar structure of the caudal segment and of the uropoda, as also the comparatively short antennae and legs. Moreover, Mr. B.-Lund has stated that the young leave their mother in a more advanced stage of development than in other Oniscoida, having all the 7 segments of the mesosome well defined. According to the same author, no marsupial pouch is formed in the female. But this may be less correct, as I have found in one specimen of Armadillidium pictum distinctly [developed incu- batory plates. Mr. B.-Lund refers to this family 8 different genera, and 2 more are added by Mr. Dollfus, increasing the number to 10 in all. Of these, only a single genus is represented in the fauna of Northern Europe. Gen. Armadillidium, Brandt, 1830. I Generic Characters. Body oblong or elliptical in form, very convex, and capable of being rolled up into a perfect ball. Cephalon with the front distinctly marginate, lateral lobes rounded, and sharply defined at the base. Epistome ver- tical, forming above a triangular shield, advancing more or less beyond the frontal edge. Side-plates of 1st segment of mesosome large, securiform, not incised behind. Metasome semicircular, with the edges continuous throughout; last seg- ment lamellar, quadrangular or triangular in form, not extending beyond the limits of the epimeral plates of the penultimate segment. Eyes distinct, lateral. Antennulse with the terminal joint but little produced. Antennae, as a rule, not attaining half the length of the body, penultimate peduncular joint scarcely longer than the 2nd ; flagellum biarticulate. Opercular plates of only the first 2 pairs of pleopoda with air-cavities. Uropoda very short, with the basal part broad, lamellar, outer ramus spatulate, inner narrow, cylindric. Remarks.- This genus, established by Brandt, is easily distinguished from Cubans (Armadillo), with which it was formerly confounded, by the non- incision of the anterior side-plates of the mesosome, and by the broad, spatulate form of the outer ramus of the uropoda. It comprises numerous species chiefly from southern Europe, amounting, according to B.-Lund, to more than 30 in all. Of these, only 4 species are represented in the fauna of northern Europe, and will be described below. 189 1. Armadillidium vulgare, Latr. (PI. LXXX1I.) Armadillo vulgaris, Latreille, Hist. Crust. Vol. VII, p. 48. Syn: Armadillo pilularis, Say. trivialis, Koch. ater, Schnitzler, uariegatus, Latr. maculatus, Risso. pustulosus, Desm. Armadillidium commutation, Brandt & Ratzeb. Specific Characters. Body oblong oval, more than twice as long as it is broad, side-contours sub-parallel, dorsal face strongly vaulted and perfectly smooth. Cephalon, seen dorsally, broadly quadrangular, transversely truncated in front, lateral lobes comparatively small, rounded. Side-plates of 1st segment of mesosome with the posterior corner acute. Metosome broad, semicircular, scarcely occupying more than l / 5 of the length of the body; last segment much shorter than it is broad at the base, and slightly tapering distally. tip transversely truncated. Antenna? very short, scarcely exceeding in length Y* of the body, flagellum about the length of the last peduncular joint, and having its 1st arti- culation somewhat shorter than the 2nd. Last pair of legs with the ischial joint rather large, equalling in length the succeeding part of the leg. Copulative ap- pendages of 1st pair of pleopoda in male with the tips slightly divergent; oper- cular plate of 2nd pair rather produced, but scarcely curved outwards at the tip. Uropoda with the outer ramus much shorter than the basal part, and very broad, its distal edge being continuous with the last segment. Colour of dorsal face somewhat variable, sometimes uniformly dark grey or nearly black, sometimes variegated with lighter patches generally arranged on the mesosome in 3 longi- tudinal rows, one median and 2 lateral; between them, moreover, on each seg- ment is a group of more or less distinct flexuous stripes. Length attaining 14 mm. Remarks. This is the first described form of the family Armadilli- diidoBj and it is even very probable that the Oniscus armadillo of Linneus may refer to this species. It may be recognised from the other known species espe- cially by the form of the cephalon and the last segment of the metasome, as also by the very broad spatulate form of the outer ramus of the uropoda. Occurrence.- The only record of the occurrence of this widely distributed species in Norway is in a short note of Dr. Aug. Hansson, who states its occurrence at Femsjo near Fredrikshald. I cannot, however, doubt that, on a closer investigation, it will be found to exist in many other parts of the country, 190 as it is very common both in Sweden and Denmark. The figures here given are from specimens kindly sent to me from the Museum of Copenhagen. Distribution. Throughout the whole of Europe and the adjacent parts of Africa and Asia; Madeira, New York, Montevideo, Melbourne. 2. Armadillidium opaeum, (Koch). (PI. LXXXIII, fig. 1.) Armadillo opacus, Koch, Deutschl. Crust, etc. 34, fig. 2. 3. Syn : Armadillidium consparsum, Zaddacli. sulcatum, B.-Lund (not M.-Edw.) Specific Characters. Very like the preceding species as to its general appearance, but of somewhat smaller size. Cephalon with the frontal margin slightly arched, and surpassed by the epistomal shield. .Side-plates of meso- some discontiguous. Last segment of mesosome very broad, bluntly rounded at the tip. Antenna; with the last joint of the fiagellum nearly twice as long as the 1st. Colour of dorsal face light grey, irregularly variegated with darker patches. Length 9 mm. h'rmarks. This species was at first confounded by B.-Lund with the Al- gerian form A. sulcatum M.-Edw.; but in a supplement to his work he has kept it apart from that species. It is very like A. vulyare, but, on a closer examina- tion, it may be distinguished by the' somewhat different form of the cephalon and of the last segment of the metasome, as also by the different colour of the body. Occurrence. From Norway this species has not yet been recorded, but, as it is not uncommon in Denmark together with A. vulgare, it is most pro- bable, that, on a closer investigation, it will be found to exist also in this country. The figures here given are from a somewhat incomplet specimen kindly sent to me from the Museum of Copenhagen. Distribution. Denmark, Germany, B< (hernia. 3. Armadillidium pietum, Brandt. (PI. LXXXIII, fig. a.) Armadillidium i>idum, Brandt. Consp. pag. 24, fig. t. Syn: Armadillidium Grubci, Zaddach. Kjx'cific Character*. - Body oblong oval or elliptical in form, with the dor-;il I;HT strongly vaulted and perfectly smooth and shiny. Cephalon with the frontal edge somewhat prominent in the middle, lateral corners comparatively small, rounded. Side-plates of 1st segment of mesosome with the posterior corner 191 acute. Last segment of metasome triangular, almost as long as it is broad at the base, and gradually tapering distally, tip obtusely pointed. Antennse short, scarcely exceeding J /4 of the length of the body, last joint of the flagelliim more than twice as long as the 1st. Last pair of legs with the ischial joint not at- taining the length of the succeeding part of the leg. Copulative appendages of 1st pair of pleopoda in male greatly produced, with the extremities very slender and abruptly curved outwards; opercular plate of 2nd pair likewise produced in the form of a hook. Uropoda with the outer ramus about the length of the basal part, and quadrate in form. Colour of dorsal face dark reddish brown, or chest- nut brown, with a double row of rather conspicuous angular yellow patches along the middle of the mesosome, and another series of lighter patches on each side, at the base of the side-plates; between this series and the dorsal patches in each segment, there is a group of less distinct flexuous stripes. Length of adult female 8 mm. Remarks. This species, first described by Brandt, may be easily distin- guished from either of the 2 preceding species by the different shape of the last segment of the metasome, as also by its beautiful colouring. The A. Grubei of Zaddach is, according to B.-Lund, identical with this species. Occurrence. I have found this form in two localities near Christiania, viz. on the Ladegaardso and at Lysaker. In the former place it occurred occa- sionally in rather dry situations below stones; in the latter it was found exclu- sively beneath loose bark. I have also received the species from Mr. Ellingsen, who found it likewise under loose bark at Kragero. There are also some specimens in our Univ. Museum from Langesund, having been collected many years ago by the late Dr. Jensen ; and B.-Lund records it also from Arendal. Finally, Dr. Aug. Hansson states its occurrence at Femsjo near Fredrikshald. It moves rather slowly, and at the slightest touch rolls its body up into a perfect ball, which is easily lost to sight in the hollows of the ground. Distribution. Sweden, Denmark. Germany, Belgium, France. 4. Armadillidium pulchellum, Brandt. (PI. LXXXIII, fig. 4.) ArmatlilliJinm pulcJiellum, Brandt. Consp. p. 26, fig. 18. Syn : Armadillo maculatus, Sill. ,. Armadillidium pictum, Plateau (not Brandt). Specific Characters. Form of body about as in A. pictum. Cephalon with the frontal edge distinctly prominent in the middle, lateral lobes evenly rounded. 192 Side-plates of 1st segment of raesosome abruptly truncated at the posterior corner. Last segment of metasome much broader than it is long, and obtusely truncated at the tip. Antennse very short, with the last joint of the flagellum nearly 3 times as long as the 1st. Legs, pleopoda and uropoda nearly as in A. pictum. Colour of dorsal face dark brown, more or less distinctly variegated with lighter patches, arranged as in the above-named species. Length of body scarcely exceed- ing 5 mm. Remarks. In its general appearance this species bears considerable resem- blance to A. pictum, and may easily be confounded with it. On a closer exa- mination, it is however found to differ very markedly in certain points, and may thus undoubtedly be regarded as specifically distinct. The peculiar form of the side-plates of the 1st segment of the mesosome is an especially marked cha- racter, and the caudal segment also differs essentially in its form. Occurrence. I have myself only met with this species in a single locality near Christiania, viz., close to the shore on the outermost point of the Ladegaardso, where it was found occasionally below stones together with Porcettio pictus. Mr. Ellingsen has, however, collected it in 3 different places, viz., at Kragero, Grim- stad and Boro, and some few specimens in our Univ. Museum were also found among A. pictum, and were collected at Langesund by the late Dr. Jensen. In habits it exactly resembles A. pictum. Dstribution. Northern and Central Europe, in the same places as A. pictum. Tribe 6. EPICARIDA. The Isopoda belonging to this tribe are all parasitic forms, and their hosts are invariably other Crustacea of different orders ; hence the above name of the tribe. They are the most degradated forms of Isopoda, and in some instances the fully-grown female represents merely a simple sac rilled with ova, and without any trace of segmentation or of limbs, so that the idea of its being a crustacean animal would hardly suggest itself, if the development were not known. In all the forms a more or less pronounced regressive metamorphosis has been observed, comprising at least two distinct larval stages, very dis- similar both in their general appearance and in the structure of the several appendages, and equally different from the adult animal. As will be shown further below, there is in all probability in most of the forms even a 3rd intermediate larval stage, the Microniscus stage, which, however, has not hitherto been recognized as such, but has been wrongly regarded as an adult form of Epicarida representing even a distinct family. The sexual dimorphism in all the forms is very pronounced. The male in all cases, as compared with the adult female, is of diminutive size, and is generally found clinging to the genital region of the female like a parasite. It is also of an appearance very different from that of the female, retaining, as it does, several of the larval characters, and in some instances it does not differ from the last larval stage except by the presence of generative organs. In certain cases (Entoniscidre), the parasite penetrates to the inner organs of its host, looking merely like an endoparasite, and in all such cases the body of the female is found to be greatly deformed. But when the parasite retains its character as a true ectoparasite, the female also exhibits, as a rule, some more or less pronounced deformity - - and is often conspicuously asymmetrical; even when the segmentation of the body is apparent. In the latter case, the 3 chief divisions, cephalon, mesosome and meta- some, may, us a rule, be tolerably well distinguished, though not very sharply defined from each other. Of appendages, the cephalon carries generally in front two pairs of rudimentary antennae, and is produced below to a conical pro- minence exhibiting on the tip the oral aperture. The oral parts are much reduced, only the mandibles and maxillipeds being distinctly developed, the for- mer being styliform and converging to the oral orifice, the latter lamelliform. The legs, when present, are all alike, prehensile, terminating in a minute hand. The pleopoda are in some instances rather large, and all of them branchial in character, whereas in the larvae these organs are natatory. The uropoda, when present, are always very small and simple, and do not in any instance form with the last segment a caudal fan. As to the systematical relation of this tribe to other Isopodous tribes, Dr. H. J. Hansen has suggested, that it is closely related to the Cymothoidce and cannot therefore be set apart from the tribe FlabeUifera. In this opinion I am, however, by no means prepared to agree with the distinguished Danish author. The apparent resemblance to the CymotlioidoR is only due to the parasitic habits of both ; but in the more essential points of organisation, as also in their develop- ment, both these groups are in reality widely different, and no transition forms between them are as yet known. Of recent authors, who have made this tribe their special study, may in the first place be named the two distinguished French naturalists M.M. Giard and Bonnier, who have published several admirable treatises on these interesting Isopoda, accompanied by excellent illustrations. It is however to be regretted, that these authors have introduced considerable confusion as to the definition of species and genera, owing to an assumption, according to which it is postulated, that one and the same species of parasite cannot be found on different species of Crustacea, and that, as a rule, parasites infesting different genera af Crustacea must also be generically different. This assump- tion is most certainly unmaintainable, and a great number of species, and - per- haps also genera founded only upon this principle, must of course be cancelled. The grouping of the several genera, into families has also to a great measure been made according to a similar principle. No less than 7 families have thus been established by the above-named authors, viz. 1. Microniscidos parasitic on Copepoda. 2. Cyproniscidce Ostracoda. 3. DajidcB Schizopoda. 4. Cabiropsidce Isopoda and Amphipoda, 5. Cryptonistidce parasitic on Cirripedia. 6. EntoniscidoB Brachyura. 7 BopyridoB. decapoclous Crustacea. Of these families, the 1st must be wholly cancelled, as only representing transitory larval stages of different Epicarida, and the 3 families Cyproniscidce, Caliropsidce and Cryptoniscidce ought to be combined into one family only, for which the name of CryptoniscHdoB may be retained. The number of families is thereby reduced to 4 in all. It is not improbable that these families in future may assume the character of superior groups, and that each of them may be again subdivided. At present, however, I consider it convenient to maintain the above-named 4 families as such. Of Entoniscidce no form has hitherto been recorded from Norway; but I regard it as beyond doubt, that, on a closer investigation, also this family will be found to be represented in the fauna of this country. Of the other 3 families several genera and species will be described in the following pages. Fam. 1. Bopyridae. Characters. Body of female distinctly segmented, more or less asym- metrical, twisted now to the right, now to the left, dorsal face flattened. Cephalon deeply sunk into the mesosome, and carrying in front 2 pairs of rudi- mentary antennae; eyes, when present, dorsal. Maxillipeds lamellar, biarticulate, obtecting the oral area below, and more frequently exhibiting a small terminal joint, and at the base 2 curved lanceolate appendages (epignaths). Legs 7 pairs, sometimes obsolete on one side, and all of the same structure, short, prehensile ; coxal plates obsolete or distinctly defined. Incubatory plates 5 pairs, more or less arching over the ventral face of the mesosome ; 1st pair, as a rule, con- cealed by the 2nd and divided by a transversal fold into 2 segments, of which the distal one projects freely within the incubatory cavity. Metasome more or less distinctly segmented, pleopoda, forming simple or double lamellae, all of the same structure, rarely obsolete. Uropoda, when present, simple, lanceolate. Male more or less slender, perfectly symmetrical, with the cephalon evenly rounded in front, and all the segments of mesosome sharply defined, those of metasome sometimes distinct, sometimes confluent. Last larval stage with the mouth 196 simple, conic; posterior antennae with the flagellum 4-articulate ; legs of uniform structure; uropoda with the inner ramus shorter than the outer. Parasitic on decapodous Crustacea. Remarks. This family comprises the more differentiated forms of Epica- rida, in which the retrograde metamorphosis is less pronounced. Yet the adult female in every case exhibits an appearance very different from that of the male and the larvae, the body being more or less deformed and asymmetrical, though its segmentation, as a rule, is distinct at least on the dorsal side, with the 3 chief divisions well defined. The greater number of forms are found as parasites in the branchial cavity of higher Crustacea ; but there are a few forms which infest the ventral or dorsal face of the metasome of their hosts, and which also in several other respects differ considerably from the others, and might therefore perhaps more properly be separated into a particular subfamily (the genera Athelges and Phryxus). Rather a great number of genera have been established, especially by M.M. Giard and Bonnier; but I believe that some of these genera are not very well defined, so that a reduction may perhaps be found to be necessary. In the following pages will be described 6 genera, at least 5 of which are stated to belong to the fauna of Norway. Gen. 1. BOpyrUS, Latr., 1804. Generic Characters. Body of female broad, flattened, rather asymmetrical, with the segments of mesosome firmly connected. Cephalon deeply immerged within the 1 st segment of mesosome, frontal edge broad, lamellar. Lateral parts of mesosome slightly elevated, subcontiguous, coxal plates inconspicuous. Meta- some narrowed, with the segments confluent in the middle of the dorsal face, epimeral plates distinct, subcontiguous, last segment resembling them. An- terior antennre distinctly 3-articulate, posterior ones apparently consisting of only 2 articulations. Terminal joint of maxillipeds well defined, broadly oval or cordiform. 1st pair of incubatory lamella rather large, divergent, distal segment terminating in a narrow linguiform lobe; the 4 succeeding pairs widely apart, leaving a -broad open space in the middle, the marsupial pouch being here closed by the carapace of the host. Legs very small, concealed within the lateral edges of the mesosome. Pleopoda simple, lamellar. Uropoda wanting. Male with the segments of metasome imperfectly defined. Parasitic in the branchial cavity of prawns. Remarks. This genus was established as early as in the year 1804 by Latreille, and may be regarded as the type of the family. We know as yet with certainty of only a single species, to be described below. Several other species, it is true, have been named by M.M. Giard and Bonnier; but none of them have been as yet described or figured in detail, and as they seem chiefly to be established according to the different species of prawns in which they were found, it is highly probable that their number will be greatly reduced and per- haps combined into one and the same species. Bopyrus sqvillarum, Latr. (PI. LXXXIV. fig. 1.) Bopyrus sqrittaruni, Latreille, Hist. Nat. Crust. Vol. VII, p. 55, PI. LIX, fig. 2. Syn. : Monocules craitgorum, Fair. Bopyrus Fougerouxi, Giard & Bonn. etc. Specific Characters. Body of female broadly oval or pyriform in outline, obtusely truncated in front, narrowly rounded behind, twisted sometimes to the right, sometimes to the left, according to its place on the host. Cephalon subtriangular in form, widening considerably distally, frontal edge nearly straight and continuous with the side-contours of mesosome, lateral corners narrowly rounded. Segments of mesosome with the lateral parts slightly elevated, each with a small indentation in front of the posterior corner, defining sutures strongly curved. Median length of metasome about half that of the preceding part of the body, epimeral plates slightly bilobed, terminal segment of exactly the same appearance as the epimeral plates. Male oblong oval in form, with the segments of mesosome well defined, those of metasome confluent along the middle. Colour of female (according to Sp. Bate & Westwood) pale greenish, with the head and incubatory lamella darker blackish. Length of female 11 mm., of male 2 mm. Remarks. This form was first recorded by 0. Fabricius as Mono- culus crangorum; but as the specific name proposed by that author involves a confusion of shrimps with prawns, it is impossible to retain it and therefore, though the older - one, it ought to give place to that proposed by Latreille. It is the only as yet known species of the genus, for the several species named by M.M. Giard and Bonnier cannot be admitted as such until it is clearly shown, that in reality they differ specifically from the type species. It is very probable, that~the present species infests several species of prawns and perhaps also species of nearly-allied genera. 198 Occurrence. This form is found parasitic in the branchial cavity of spe- cies of Leander (Palsemon), such as L. scrratus, squilla and Eathfcei, sometimes on the left, sometimes on the right side, in every case causing a strong lateral tuber- osity of the carapace, similar to that caused by Bopyroldes liippolytes (fig. 2 x). It has not yet been recorded from Norway; but as at least 2 of the species of Lei'ut-ilrr, which at times are infested by this parasite, are very common on our coasts, it is most likely that, on a closer investigation, it will be found to belong to the fauna of Norway. The figures of the female here given are from a specimen found on Leander serratiis from the Danish coast; that of the male is copied from Sp. Bate and Westwood's work. Distribution. Danish coast (Meinert), British Isles (Sp. Bate), coast of France (Giard & Bonnier), Mediterranean. Gen. 2. BOpyrOideS, Stimpson, 1864. Syn : Bopyrus, Kroyer (not Latreille) Gyge, Sp. Bate (not Corn. & Pane.) Generic Characters. Body of female resembling that of Bopyrus, though having the cephalon less broad, the lateral parts of mesosome perfectly smooth, and the metasome distinctly segmentated. Posterior antennae 4-articulate. Terminal joint of maxillipecls well defined, but rather narrow. 1st pair of incu- batory plates concealing the whole ventral face of cephalon, and having the distal segment broadly securiform; the succeeding pairs, as in Bopyrus, widely apart. Legs short, more or less concealed within the lateral margins of the mesosome. Pleopoda obsolete, being replaced by slight fleshy ridges. Uropoda wanting. Mtdc with the segments of metasome fused together. Parasitic in the branchial cavity of species of the genus kpirontocaris (Hippolyte). BemctrJcs. This genus, established by Stimpson, is nearly allied to Bopyrus, from which it is chiefly distinguished by the absence of true pleopoda, and by the male having all the segments of metasome fused together. The species of this genus are found parasitic in the branchial cavity of different Carida belonging to the genus Spirontocaris Sp. Bate (Hippolyte Kroyer). To the fauna of Norway belongs only a single species, to be described below. 199 Bopyroides hippolytes, (Kr0yer). (PI. LXXXIV, fig. 2). Bopynis hippolytes, Kreyer, Gronlands Amphipoder, p. 78, PI. 4, fig. 22. Syn. : Gyge hippolytes, Sp. Bate & Westw. Specific Characters. Body of fully grown female broadly oval, rather asymmetrical, being curved to the right or left, according to its place on the host; dorsal face much flattened and very smooth. Cephalon almost semicircular in form, and deeply immerged within the mesosome, frontal edge nearly straight, lateral corners obtusely pointed. Segments of mesosome firmly connected, with the lateral parts perfectly smooth, contiguous, and without any marginal indenta- tions. Metasome comparatively short, its median length scarcely exceeding 1 /s of that of the proceeding part of the body, sutures between the segments much curved and distinct also in the middle of the dorsal face, epimeral plates con- tiguous, truncate at the tip, last segment likewise truncate. Male very slender, linear, 4 times as long as it is broad, segments of mesosome very sharply marked oft' from each other, metasome forming an undivided obtusely conical piece. Colour of female whitish, with the incubatory plates dark violet. Length of female reaching to 11 mm., that of male to 272 mm. Remarks. This form was first described by Kr0yer as Bopynis hippo- lytes, and was subsequently referred by Sp. Bate and Westwood to the genus Gyge of Cornalia and Panceri. It must, however, unquestionably find its place within the genus Bopyroides of Stimpson, and it is indeed somewhat questionable, if the species of Stimpson, B. acutimarginata, is not identical with the North European form. In its general appearance and its mode of infesting its host, the female of this Bopyrid bears a great resemblance to Bopynis squillarum, but may, on a closer examination, be easily distinguished by the distinct segmentation of the metasome, and by the want of true pleopoda, the latter being replaced by very slight, fleshy ridges. The male, moreover, distinguishes itself by its very slender form and the complete fusion of the segments of the metasome. Occurrence. I have met with this form along the whole Norwegian coast, from Vads0 to the ChristianiaFjord. It is found parasitic in the branchial cavity of 3 different species of the genus Spirontocaris Sp. Bate (Hippolyte Kr0yer) ; viz., S. polaris, in which species it was first found by Kr0yer, S. spinus and S. securifrons. I have very carefully compared specimens from all these 3 species, and have not been able to find any difference between them. When 200 fully grown, the parasite causes a very large and conspicuous rounded tuber- osity on the carapace of its host, occurring sometimes on the left, sometimes on the right side (see fig. 24). The walls of this tuberosity fit exactly around the sides of the parasite, and the very capacious marsupial pouch is thereby completely closed, the incubatory plates extending only for some distance up the sides of the cavity. As is the case with most other Epicaricla, the parasite in- variably turns its head backwards in relation to its host, and the dorsal face towards the body of the latter. Such a position is in this instance of essential significance for the aeration of the marsupial cavity, the water washing the branchial cavity of the host from behind forwards being thus easily introduced into the marsupium of the parasite from between the 1st pair of incubatory plates. The number of ova contained in the marsupium is immense, and may amount to several thousand in all. I have observed the embryo in its last stage of development, immediately proceeding the 1st free larval stage, and have found it to agree exactly with that of Phnjxus abdominalis, as represented in PI. 91. The male is found clinging to the ventral face of the metasome of the female, just behind the last pair of incubatory plates, being generally placed trans- versally to the axis of the female. Distribution. Greenland (Kroyer), Barents Sea (Hoek), British Isles (Sp. Bate). Gen. 3. PseudlOne, Kossman, 1881. Syn. : Palcegyge, Giard & Bonn (part). Pliry.nis, Sp. Bate & Westw. (part). Generic Characters. Body of female oval or pyriform in outline, more or less asmymetrical, with the segments both of mesosome and metasome very sharply defined. Cephalon distinctly marginate in front. Segments of mesosome with the lateral parts elevated and divided by a transverse groove into 2 lobes; coxal plates well defined, though rather small, discontiguous. Epimeral plates of metasome more or less projecting, lamellar; last segment very small. Antennae and oral parts as in Bopyroides. 1st pair of incubatory plates with the distal segment produced to a narrow linguiform lobe, as in Bopyrus; the succeeding pairs large, arching over the ventral face. Legs more or less projecting later- ally, and of usual structure. Pleopoda well developed, biramous, rami lanceolate, 201 smooth or tuberculated. Uropoda distinct, forming a pair of simple lanceolate lamellse. Male with all the segments of the body well defined. Parasitic in the branchial cavity of Anomura, Macroura and Carida. Remarks. From the 2 preceding genera, the present genus is clearly distin- guished by the presence in the female of distinctly defined coxal plates, of rather fully developed pleopoda, and of distinct though simple uropoda. Moreover, the incubatory plates are much larger, so as to encompass the marsupial cavity more or less completely. Finally, the metasome of the male is as distinctly segmen- ted as the mesosome. Several species of this genus have been established, some of which, however, are referred by M.M. Giard and Bonnier to their genus Palcegyge. To the fauna of Norway belong 9 species, to be described below. i. Pseudione af finis, G. 0. Sars. (PL LXXXV, fig. 1). Pleuroorypta ajfinix. G. 0. Bars. Oversigt over Norges Crustaceer I, p., 68, PI. 2, figs. 7, 8. Syn. : Palcegi/ge affinis, Giard & Bonn. Hoi/lii, Giard & Bonn. Specific Characters. Body of female but slightly asymmetrical, oblong oval in outline, with the greatest width in the middle. Cephalon semicircular, convex above, and encircled in front by a broad arched lamella. Segments of mesosome very sharply defined in the middle, lateral parts distinctly bilobed, anterior lobe somewhat elevated and transversely truncated at the tip, posterior narrowly rounded ; coxal plates distinctly projecting, lamelliform. Metasome comparatively short, but rather broad, epimeral plates rounded, sub-imbricate ; last segment very short. Eyes distinctly perceptible, though very small and simple in structure. Terminal joint of maxillipeds well defined, narrow, incurved, setous on both edges. 1st pair of incubatory plates with the terminal lobe straight; the succeeding pairs not completely overlapping each other in the middle. Legs more fully developed than in most other species, and distinctly projecting on each side. Pleopoda with the lamellse quite smooth and partly projecting beyond the edges of the epimeral plates. Uropoda resembling in size and structure the lamellse of the pleopoda. Male rather broad, depressed, not nearly 3 times as long as it is broad, metasome not abruptly contracted, last segment minutely bilobed. Colour of female (according to notes left by my late father) whitish, with the incubatory plates dark brownish violet at their bases, somewhat lighter in their outer part; colour of male light yellowish. Length of female 10 mm., of male 2 mm. 26. Crustacea. _202_ . This Bopyrid was first described by the present author as ffin is. It was subsequently referred by M.M. Giard and Bon- nier to their genus 7 \/ la '////// t j , the type of which is P. Barrel, found on a fresh- water prawn (Palsemon dispar) from the 'Indian Archipelago. On comparing the figures and description given by the above named authors, I find, however, that this form differs in several points very essentially from the one here treated of, exhi