Annals of fl,,> South African Museum. 



of the tail-piece. A third species belonging tu this genus has been 

 added recently by the same author from Paraguay. 



Occurrence.- -This form was originally described from specimens 

 reared from dried mud taken at Knysua. It did not develop from any 

 of the other parcels of mud subsequently received. 



Distribution .South America. 



GEN. 14. PLEUROXUS, Baird. 



Remarks. -The species of this genus are recognised by the more or 

 less pronounced trigonal form of the shell, and the strongly produced 

 acuminate rostrum, which admits of being closely appressed to the 

 anterior part of the valves. About twenty species'have been recorded 

 from different parts of the world, one of them being also represented 

 in the fauna of Cape Colony. 



42. PLEUROXUS INEEMIS, G-. 0. Sars. 



(Plate XLI, figs. 2, 2 a, 6.) 



Pleuroxus inermis, G. O. Sars. Fresh-water Entomostraca from the 

 neighbourhood of Sydney. Arch, f . Math. u. Naturv. 1896, p. 31 pi 5 

 figs. 8, 9. 



Specific CharactersFemale. Shell, seen laterally, oval trigonal in 

 outline, with the dorsal margin boldly arched in the middle, ventral 

 slightly flexuose and protuberant in front of the middle ; posterior ex- 

 tremity somewhat exserted and narrowly truncated, with the upper 

 corner well marked, the lower obtuse and without any obvious 

 denticles. Head comparatively short and strongly procumbent, ter- 

 minating in a long and sharply pointed rostrum, pointing obliquely 

 backwards. Anterior part of valves sculptured with a number of very- 

 conspicuous arched striae running parallel to the anterior edges'; 

 posterior part smooth, or with a very faintly indicated reticulation.' 

 Ocellus much smaller than the eye and far remote from the tip of the 

 rostrum. Antennulae comparatively small, scarcely extending beyond 

 the middle of the rostrum. Tail-piece of moderate size, with the anal 

 sinus well marked; distal part slightly narrowed and shallowly 

 incised at the end ; supra-anal angle very slight ; marginal denticles 

 comparatively small, about fifteen pairs ; apical claws rather strong, 

 each with two unequal denticles at the base. 



Length of shell about O55 mm. 



Remarks. This form was described under the above name in 1896 

 by the present author from Australian specimens. It is closely allied 



