PRESTON: ON MOLLUSCA FROM ZAMBESI RIVER. 301 



Alt. 10-5 mm. ; diam. maj. 7 mm. Aperture, alt. 5 mm. ; 

 diam. 3 mm. 



Hab. — Just above Victoria Falls, Zambesi River. 



Var. cosTATA. Fig. 4. 



Shell more globular than the type ; the upper whorls transversely 

 ribbed ; the dark bands increasing to five on the body- whorl. 

 Alt. 9-5 mm. ; diam. maj. 7-25 mm. 



Unio Zambesiensis, n.sp. Fig. 1. 



Shell subtrapezoidal, deep rich brown, sculptured, especially above, 

 with wavy zigzag ridges, and below with coarse irregular concentric 

 lines of growth; anterior side obliquely rounded; posterior side 

 somewhat squarely rounded. 



Alt. 22-5 mm. ; length 35 mm. 



Hab. — Just above Victoria Falls, Zambesi River. 



All the species collected are much eroded at the apex, the erosion 

 extending, notably in Melania and Cleopatra^ down the whole of one 

 side of the shell. 



