The Fresh-water Entnt<>*tritr<i of Cape Province. 337 



slightly prominent aud occurring near the middle of the piece ; 

 marginal denticles very small, sub-marginal combs well marked, about 

 ten on each side ; apical claws of moderate size, with the basal denticle 

 rather slender. 



Body very pellucid, with a faint yellow tinge. 



Length of shell scarcely exceeding 0'35 nun. 



Remarks. I think I am right in identifying the above-characterised 

 small Alona with the species recorded by Welthner from East Africa. 

 The description and figures given by that author are certainly rather 

 unsatisfactory, and it is even possible that several nearly allied species 

 have been confounded by him ; but on the whole I cannot see any 

 reliable difference, and the measurements of the shell given (O24-O35) 

 agree fairly well with those of the present species, which, indeed, is 

 by far the smallest of the South African species of Alona. 



Occurrence. This form developed very abundantly in several of my 

 aquaria prepared with mud partly from Port Elizabeth, partly from 

 the neighbourhood of Cape Town. 

 Distribution. East Africa. 



37. ALONA KARUA, King. 

 (Plate XL, figs. 4, 4 a.) 



Alona kariia, King. L.c. 1852, p. '260, pi. viii d. 



Syn. : AloneUa Jcarua, Gr. 0. Sars. 

 ,, Alona miilleri, Richard. 

 ,, Leydigia quadridentata, Brady. 



Specific Characters Female. Shell, seen laterally, irregularly quad- 

 rangular in outline, with the dorsal margin considerably arched in the 

 middle, ventral straight in its posterior part, but conspicuously ascend- 

 ing anteriorly ; posterior extremity somewhat obliquely truncated, with 

 the upper corner well marked, lower rounded off. Head less procum- 

 bent than in most other species, with the rostral corner rather promi- 

 nent and pointing obliquely forwards. Surface of valves sculptured 

 with very distinct and somewhat oblique striae, crossed in the anterior 

 part of the valves by a number of arcuate ridges running parallel 

 to the anterior edges ; inferior edges, as usual, densely setiferous, and 

 exhibiting, moreover, just in front of the infero-posteal corner, a row of 

 three to five small denticles. Ocellus smaller than the eye, and located 

 much nearer to it than to the tip of the rostrum. Anteuuulae not 

 nearly extending so far as the latter. Tail-piece comparatively short, 

 but rather broad, widening somewhat distally, with the infra-anal 

 margin evenly curved throughout ; supra-anal angle very slight, and 



