612 ox CRUSTACEA BROUGHT BY DR WILLEY FROM THE SOUTH SEAS. 



a distinct species. This I am strongly disposed to believe to be the fact, since the 

 two specimens about to be described present parallel differences, but are clearly distinct 

 species, being both males. Should N. Suhmii prove to be a name covering two species, 

 it ought to be reserved for the female specimen, since Sars according to his custom 

 gives precedence to the description of that sex. The male specimens will then require 

 a fresh designation, in respect of which a suggestion will be made presently. 



N.\.N"X.\STACUS OSSIANI n. Sp. 



Plate LXIV a. 



Carapace tumid, median line sinuous, its concavity flanked by lateral convexities. 

 Pseudo-rostral projection forming a rather broad, apically rounded process, obliquely 

 ascending, the distal part concentrically ridged. Antero-lateral corners blunt, very little 

 produced. Lower and hind margins forming almost a right angle, corner rounded. 

 Surface reticulate with he.xagonal or .scale-like markings. Fourth and fifth of the free 

 peraeon segments with dorsal centre strongly raised. Segments of pleon with pellucid 

 lateral carinae, as if formed by o\erlapping scales, and pair of serrate dorsal carinae 

 distally produced into a strong tooth in each of the first five segments; fifth segment 

 not greatly longer than the rest. 



Eyes apparently having three facets, which are difficult to distinguish owing to 

 the darkness of the accompanying pigment. 



The first and second antennae scarcely differ from those of jVannastacus iniguicu- 

 , latii^, described in detail by Sars (Middelhavets Cumaceer, pp. 165, 169), except that 

 the slender flagellum of the second pair is much shorter, consisting of ten joints 

 instead of eighteen. 



The mouth-organs and peraeopods, as is perhaps sufficiently shown by the figures, 

 are in close agreement with those of N. unginculatus. The branchial apparatus of the 

 first maxillipeds was not, however, clearly observed. 



The uropods are imperfect, but have peduncles shaped like those of X. unguiculatus, 

 a little less produced beyond the terminal segment. The spine of the outer ramus is 

 perhaps relatively a little .shorter, but with the apex broken this remains uncertain. 



Length, 2 mm. 



Habitat. " Barawon. Auftrieb at night, lO/S/9.5." One specimen, male. Dr Willey 

 informs me that Barawon, where this plankton capture was made, is a small village at 

 the entrance to Blanche Bay, New Britain. 



Though the shape of this species so much recalls that of iV. Suhmii, that at the 

 first glance I made little doubt of their identity, this is separated from that not only 

 by characters of the trunk and pleon, which might be sexual, but also by the pro- 

 portions of the joints in the fifth peraeopods and outer ramus of the uropods, which 

 in the one case Sars' figure and in the other his figure and description show to be quite 

 different. 



