406 Annals of the South African Museum. 



Locality. BufEel's Bay (False Bay). 1/3/15. (K.H.B.) 1 $. Low- 

 tide. (S.A.M. No. A3372.) 



The chief peculiarities of this species are iu the 1st pleopods and the 

 1st peraeopods, the latter bearing at first sight a strong likeness to the 

 gnathopod of an Amphipod. 



GEN. HAPLONISCUS Rich. 



1908. Haploniscus Richardson, Proc. U.S. Nat, Mus. vol. 35 [1909], 



p. 75. 



1914. Vanhoffen, Deutsch. Siidpol. Exp. xv, 4, p. 557. 



1916. ,, Hanseu, Dan Ingolf Exp. iii, 5, p. 28. 



This genus was instituted to receive a species from the Arctic 

 ocean described by Sars as Nannoniscus bicuspis but which differed 

 in several respects from the type-species, N. obloiujus. At the same 

 time Miss Richardson added two new species from deep water off the 

 Atlantic coast of N. America. 



There is one interesting feature in this genus which has not been 

 commented upon by either Sars or Miss Richardson, namely, the 

 structure of the telsou. The lateral portions of the ventral surface 

 have grown over and completely fused, if one may so express it, so as 

 to form a chamber containing the 3rd-5th pleopods. 



This chamber in the species described below is spacious owing to the 

 high vaulting of the ventral surface ; in the other species it is impos- 

 sible to tell from the figures whether this surface is vaulted or not. 



A somewhat similar chamber, containing the 2 pairs of maxillae 

 and the mandibles, is formed by the sides of the head and closed in by 

 the maxillipeds with their epipods, leaving a small aperture in front 

 through which the food can enter. 



The structure of the telson and probably also of the " buccal " 

 chamber may be interpreted as an adaptation to habitat. All the species 

 of the genus live at great depths, and although the nature of the bottom 

 is not recorded in the case of the previously known species, it may 

 be assumed to be a fine mud as in the case of the present species. 

 Contrary to expectation there are no plumose straining setae round 

 the edges of the operculum. There are a few widely spaced simple 

 setae on the outer margin of pleopod 2 in <$ , and on the operculum 

 in 9 . The anal opening is quite separate from the branchial chamber. 



HAPLONISCUS DIMEROCEEAS n. sp. 

 (Plate XVII. Figs. 4-7.) 



Body nearly parallel-sided, whole of the dorsal and sternal surfaces 

 minutely and closely pitted. Head about twice as broad as long, 



