746 rnoF. o. o. saus on* [May 3, 



Length of shell 0'52 mni., height ()'2() nini., width 0'21 mm. 



Remarks. — This form may be easily recognized by its com- 

 paratively narrow reniform shell, and more paiticularly by the 

 peculiar delicate seri-ations occuri-iiig on the posterior corners of 

 both valves, a character from which the specific name here 

 proposed has been derived. 



Occurrence. — Of this species also only a single specimen has 

 been secured, a fully grown female. It was found in a. sample 

 from Tanganyika (IGD), taken 18/11/04 at Kala (E. shore of 

 lakt'). 



19. CVPUIDOPSIS BIUENTATA, sp. u. (Plate LXXI. figs. 1-3.) 



Sppcijic Characters. — Fkmale. Shell moderately tumid ; seen 

 laterally (fig. 1) rounded triangular in shape, greatest height 

 occurring in the middle and considerably exceeding half the 

 length, Ijoth extremities obliquely rounded and somewhat deflexed, 

 the posterior one more blunted than the anterior, dorsal margin 

 boldly arched and sloping more steeply to the anterior than to 

 the posterior extremity, ventral margin nearly straight ; seen 

 dorsally (fig. 2) subovate in form, greatest width about half the 

 length and occurring behind the middle, anterior extremity 

 narx-ower than posterior. Valves slightly unequal, the left over- 

 lapping the right along the anterior extremity, as also at the 

 lower part of the posterior one, hind corner of this valve armed 

 with two recurved dentiform processes (fig. 3) similar to that 

 found in C. monodonta. Surface of shell smooth, but i-ather 

 densely hairy at each extremity. 



Male of about same size as female and exhibiting a similar 

 shape and armature of the shell. 



Length of shell 0-49 mm., height 0*29 mm., width 0*23 mm. 



Remarks. — This form somewhat resembles C. mo)io(lonta in the 

 shape and armature of the shell, but is of considerably larger size, 

 tind is, moreover, distinguished by the presence of two dentiform 

 processes, instead of a single one, at the posterior corner of the 

 left valve. 



Occurrence. — Two s[)ecimens of this form, a male and a female, 

 were found in a sample from Tanganyika (97), taken 19/9/04 at 

 Niamkolo (S. end of lake). 



20. Cypridopsis tumidijla, sp. n. (Plate LXXI. figs. 4-6.) 

 Specific Characters. — Fkmalk. Shell unusually tumid; seen 



laterally (fig. 4) of oval reniform shape, greatest height occurring 

 somewliat in front of the middle and scarcely exceeding half the 

 length ; anterior extremity obliquely rounded, po.sterior scarcely 

 narrower and blunted at the end ; dorsjil margin somewhat 

 irregularly curved, sloping more steei)ly in front than liehind, 

 ventral margin distinctly concave in tiie middle : seen dorsjUly 

 (fig. 5) ovati" in form, greatest height exceeding half the length and 

 occurring al)f)ut in the middle, anterior extremity narrower than 

 iiosterior. X'alves rathei' unei|Ual. the left one coiisiilcraMy ovei'- 



