12 



the tip of the apical spine, is considerably greater than the vertical depth of the somites 

 themselves. On the fifth somite the processes are much lower and of different form, with a 

 prominent spine on the posterior margin. The lateral groeve on the abdominal somites is well 

 developed. The lateral crests overhanging it are prominent and obscurely serrated. 



The antennae have the peduncle a little stouter than in N. unguiculatus. The proportions 

 of the legs differ very little from those of the species named. 



Uropods, (text-fig. i ^.) excluding the apical spines, about equal in length to the last 

 two somites together. Peduncle very short, its outer margin about "Z., the length of the endopod 

 which is finely serrated internally and has an apical spine about Vs of its own length. Exopod 

 nearly half the length of endopod, its basal segment nearly concealed, apical spine about equal 

 in lenofth to the ramus. 



t> 



Occurrence. Station 37. Several specimens. Station 41. Plankton. One specimen. 



Remarks. This peculiar form is distinguished from all the known species by the 

 remarkable armature of the abdominal somites. A somewhat similar armature, though less 

 strongly developed, is found in N. ossiani Stebbing, but that species appears to be distinguished 

 by having, among other characters, the pseudorostrum turned upwards and marked by concentric 

 ridges, the surface of the carapace smoother, without the bilobed dorsal process posteriorly and 

 the last two thoracic somites with a median dorsal prominence. The species was first detected 

 by Dr. H. J. Hansen who found it, with several of the other species discussed in the present 

 Report, in examining plankton material for Schizopoda and when forwarding the specimens to 

 me remarked on the peculiar characters which they presented. 



2. Nannastacus suhmii Sars. 



Nannastacus sulunii G. O. Sars, Rep. Challenger Cumacea, p. 63, pi. X, figs. 4 and 5. 



I refer to this species, not without some hesitation, a considerable number of male 

 specimens which agree in general characters with the type-specimens in the Challenger collection. 

 I have previously pointed out (Herdman's Rep. Ceylon Pearl Fisheries, Royal Society, Pt. II, 

 p. 177, 1904) that S.A.RS' figure of the male is incorrect as regards the antero-lateral angle of 

 the carapace. In the type specimens this is not produced but forms nearly a right angle, broadly 

 rounded off at the apex. In the Siboga specimens it is still more rounded and is armed with 

 a single curved tooth which I cannot find in the type-specimens. The uropods are almost 

 e.xactly one-quarter of the length of the body in the Siboga specimens while in the types the 

 proportion is distinctly less. In the Siboga specimens the terminal spine of the exopod of the 

 uropods extends beyond the middle of the endopod. In the types it is much shorter, hardly 

 exceeding one-quarter of the length of the uropods. Finally the Siboga specimens reach a length 

 of 2,6 mm. while the type specimens are about 1,9 mm. long. 



Stebbing's ^V. geoj^gi (Willey's Zool. Results, Pt. V, p. 613, pi. LXIVi?) so far as can 

 be gathered from his description and figures, agrees very closely with the present specimens. 

 The only difference of importance is that the last thoracic and first abdominal somites are stated 



