CUMACEA. 177 



peduncle very short, with a serrate crest on the dorsal surface ; endopod ahout tliree 

 times as long as the peduncle, serrate on the inner edge, and having an apical spine 

 nearly two-thirds of its own length, with two short spines at its base internally; 

 cxopod nearly half as long as the endopod, apical spine one and a half times the 

 length of the ramus. 



Locality. Gulf of Manaar, 2f miles south-south-west of Chilavaturai, depth 

 2 fathoms ; 1 specimen. 



This species resembles generally the male of N. unguiculatus, but differs in the 

 smoother carapace, in the antero-lateral angle, not serrate, but having a single apical 

 spine, in the group of spines below the pseudorostrum, and in the greater relative 

 length of the exopod of the uropods. The N. ossiani described by Mr. Stebbing 

 (Willey's ' Zool. Results/ Part V., Crustacea, p. 612) resembles the present species 

 in the concentric ridges of the pseudorostrum, which, however, appear to be much 

 more strongly marked than in our specimen. It differs in the stouter abdomen, in 

 the more pronounced dorsal depression of the carapace, in the last two thoracic 

 somites, which have the " dorsal centre strongly raised," without the double dorsal 

 crests, and in the absence of the group of spines below the pseudorostrum. Owing 

 to an accident to the present specimen I am unfortunately unable to state exactly 

 the relative proportions of the segments of the last pair of legs. As far as could be 

 seen in the undissected specimen, however, the difference in length between the 

 carpus and propodus was less than in N. ossiani. Mr. Stebbing compares his species 

 with the female of Saks' N. suhmii, which he suggests may be specifically distinct 

 from the male with which Sars has associated it. The arguments given in favour 

 of this suggestion are not very conclusive, and in particular Mr. Stebbing's remark 

 that in N. unguiculatus " the sexual dimorphism so common in the present order is 

 less striking than usual" does not seem at all applicable to that species. A re- 

 examination of the type specimens of N. suhmii in the "Challenger" collection 

 does not support Mr. Stebbing's suggestion. The specimens, in consequence of the 

 Canada balsam becoming opaque, have had to be removed from the slide on which 

 they were mounted and are therefore more accessible for examination than formerly. 

 I find that the male specimens almost certainly belong to two species, but that the 

 larger and better preserved among them, which alone correspond with Sars' figure 

 (except that the antero-lateral angle of the carapace is less narrowed and produced 

 than is there shown), agree with the female specimen and differ from all the species 

 of Nannastacus hitherto described in the extreme reduction of the exopod of the 

 uropods. In the males this ramus, including its terminal spine, does not exceed one- 

 fourth of the total length of the endopod. 



2 A 



