Mollusca from Central Africa. 61 



Unio gereti, sp. n. (Fig- 9.) 



Shell ovate, somewhat tumid, covered with a dark brown 

 silky periostracum and sculptured with fine rather closely set 

 concentric lines of growth ; umbones slightly eroded, promi- 

 nent ; dorsal margin nearly straight ; ventral margin scarcely 

 rounded ; anterior side angled above, obtusely rounded below ; 

 posterior side sloping obliquely, sharply rounded below ; 

 lateral teeth short anteriorly, elongately curved posteriorly ; 

 anterior cardinal tooth in right valve short, rather square, 

 erect, jagged, incised on the outer side; median cardinal 

 tooth very small ; posterior cardinal rather small, projecting; 

 anterior cardinal in left valve bluntly triangular, incised 

 posteriorly ; posterior cardinal bifurcate, thus presenting the 

 appearance of a double tooth ; anterior adductor scars ovate, 

 well impressed ; posterior adductor scars moderately im- 

 pressed ; interior of shell pale bluish white, somewhat 

 iridescent. 



Long. 36*5, lat. 61 mm. 



Hab. Lake Tanganyika. 



Unio mashonce, sp. n. (Fig. 10.) 



Shell elongately ovate, rather tumid, covered with a dark 

 blackish-brown periostracum, sculptured with somewhat 

 coarse and irregular concentric stria?, angled posteriorly ; 

 umbones rather large, prominent though much eroded ; 

 dorsal margin nearly straight; ventral margin almost straight, 

 but very slightly constricted towards the middle ; anterior 

 side rounded above, sloping below ; posterior side produced, 

 bluntly acuminate; anterior lateral teeth very short; poste- 

 rior laterals long and coarse ; cardinal teeth in right valve 

 wedge-shaped, solid in left valve, broad, serrated ; anterior 

 adductor scar ovate, moderately deep ; posterior adductor scar 

 narrowly fan-shaped, well impressed ; palleal impression 

 coarse, nacreous, pinkish in colour ; outer margins of interior 

 of shell nacreous, bluish white. 



Long. 80, lat. 37*5 mm. 



Hab. A sluit about 16 miles from Eukeldoorn, Mashonaland 

 (Miss Ella Sharpe-Youngs). 



Type in British Museum. 



Unio shireensis, sp. n. (Fig. 11.) 



Shell ovate, moderately tumid, covered with a pale, reddish- 

 brown, rather thin periostracum. which becomes thicker, 



