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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 tlte 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 2V2 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 Vana longiremis 

 seem to differ in some few points, I cannot doubt that he has had before him 

 the very same species. 



Occurrence. — I first detected this peculiar form in the inner part of the 

 Christiania Fjord, at a depth of 15 — 20 fathoms, and have subsequently found 

 it, though rather sparingly, also in several other localities of the Norwegian coast 

 up to the Lofoten Islands. 



Distribution. — Kattegat (Meinert). 



Gen. 3. ISChnOSOma, G. 0. Sars, 1866. 



Generic Characters. — Body extremely narrow, with the 4th and 5th seg- 

 ments of mososome firmly connected, and together forming a slender hourglass- 

 shaped 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 antennas more fully 

 developed than in the other Desmosomidas, with the flagellum distinct. Inferior an- 

 tennae long and slender, and of same structure in the two sexes. Mandibles 

 without palps, molar expansion well developed, cylindric. Penultimate joint of 

 the palp of the maxillipeds not produced at the tip. First pair of legs in both 

 sexes prehensile, with the carpus greatly expanded; the other pairs simple, am- 



