- 328 - 

 Sphaerium Iredatei, sp. n. — PI. XVII, fig. 3. 



Shell roimdl}^ ovate, moderately convex, olive green, both valves sculp- 

 tured with rather fine, closely set, concentric ridges; umbones somewhat 

 large, not prominent; dorsal margin arched; ventral margin very gentl}' 

 rounded; anterior side sloping above, rounded below ; posterior side abruptly 

 descending; anterior latéral teeth in both valves strong, sloping abruptly 

 downwards and then curving upwards again to the margin of the shell ; 

 posterior latéral teeth strong in both valves, only very slightl}^ curving 

 downwards and upwards, rather sinuous; interior of shell white towards 

 tlie umbonal région, ashen gre}^, spotted and blotched with white below. 



Long. 6.5, lat. 8.75 mm. 



Hab. — Kisumi, Lake Victoria Nyanza, British East Africa 

 (Robin Kemp). 



Sphaerium naivashaense, sp. n. — PL XVII, fig. i. 



Shell ovate, thin, gloss)', yellowish brown, both valves rather indistinctly 

 and distantl}', concentrically striate ; umbones large, somewhat flattened ; 

 dorsal margin sloping on either side ; ventral margin anteriorty rounded; 

 anterior side abruptly descending in a slight curve ; posterior side somewhat 

 produced, rounded ; anterior and posterior latéral teeth in both valves weak, 

 curving round the margin of the shell, but not sloping upwards or down- 

 wards; muscular scars in botli valves well marked; interior of shell pale livid 

 flesh colour. 



Long. 7.25, lat. 9 mm. 



Hab. — Lake Naivasha, British East Africa (Robin Kemp). 



