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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, 



