The Fresh-water E-i>ttnin>#fr<ir<t of Cape Province. o4:-! 



to the European species P. a<f/nici<* (Juriue), exhibiting a very similar 

 sculpture of the valves, but is at once distinguished by the absence of 

 the strong denticles occurring in that species at the infero-posteal 

 corners of the valves ; hence the specific name proposed. 



Occurrence. Several specimens of this form were picked out from 

 an alcoholic sample taken by Dr. Purcell from a pond in the Cape 

 Flats and kindly sent to me for examination. It was not reared in any 

 of my aquaria. 



Distribution. Australia. 



GEN. 15. DUNHEVEDIA, King. 



Si/ ii. : Crepidocercus, Birge. 



Remarks. This is a very distinct genus, being especially charac- 

 terised by the tumid shell, the greatly prominent cephalic foruix, and 

 the peculiar structure of the tail-piece. It contains as yet only a 

 very limited number of species, one of which is represented in the 

 fauna of Cape Colony. 



43. DUNHEVEDIA CRASSA, King. 

 (Plate XLI, figs. 3, 3 a-c.) 



Dunhevedia crassa, King. L.c., 1852, p. 261, pi. vii f. 



Specific Characters Female. Shell very tumid, seen laterally 

 irregularly oval in outline, with the dorsal margin boldly arched, the 

 ventral nearly straight, or slightly flexuose, and forming at the 

 junction with the anterior edge a broad, somewhat projecting curve, 

 posterior extremity slightly exserted and narrowly truncated, with the 

 upper corner well marked, the lower rounded off and armed in front 

 on each valve with a well-marked, somewhat defiexed denticle. Head 

 very broad as seen dorsally or ventrally, and somewhat procumbent, 

 with the rostral corner acute and curved downwards. Surface of 

 valves smooth, without any obvious sculpture, inferior edges densely 

 fringed with finely ciliated setae. Eye rather fully developed, with a 

 number of very conspicuous crystalline bodies projecting in front of 

 the dark pigment ; ocellus much smaller and located a little nearer to 

 the eye than to the tip of the rostrum. Antennulae not nearly 

 extending as far as the latter. Lip-plate with the edge quite 

 smooth. Tail-piece almost boat-shaped, being abruptly bent at the 

 base, with the posterior edge bulging in the middle, below the anal 

 fissure, to form a broadly rounded heel-shaped protuberance ; distal 

 part of the piece gradually tapering to an obtuse apex, and clothed on 



