188 ME. E. B.XEWTOIN' OX 15TOX-MAEIXE MOLLUSCAK" [June 1914, 



the group is so well represented in the waters of the Victoria Nyanza 

 at the present day. 



The more abundant shells are the freshwater genera Ampullaria, 

 Lanistes, and Cleopatra ; whereas the remaining or terrestrial 

 forms are few, and appear to be extremely rare. So far as past 

 distribution is concerned, only three of the species have been pre- 

 viously recorded from geological deposits : namely, Ampullaria 

 ovata and Lanistes carinatus, both of which occur in the late post- 

 Pliocene beds of Egypt (Fayum) ; and also Tropidopliora nyasana^ 

 which has been found in beds of similar age on the Lake Nyasa 

 plateau. Among the- freshwater forms, only the Ampullaria is 

 known as living in the Victoria Nyanza, while the nearest water 

 for Lanistes carinatus appears to be the Tana River, a consider- 

 able distance east of that lake. Lake Rudolf and the Mombasa - 

 Zanzibar waters are the nearest available regions for obtaining 

 Cleopatra bulimoides, while C. exarata is found only in the last- 

 named district. The land-shells are mostly restricted to the Nile 

 and lake countries of Eastern Africa. In the following table the 

 distribution is set out more fully : — 



Table showing the Distribution of the Shells collected by Db. Oswald. 



Genera and Species. 



Fossil. 





CD CS 



2-> >. 



no rl 

 o 



O-i 



Freshwater. 



Ampullaria ovata X 



Lanistes carinatus X 



Cleopatra bulimoides X 



Cleopatra exarata ; X 



Terrestrial. 



Tropidopliora nyasana .. 



Achatina sp 



Surtoa cf . nilotica 



Cerastus cf. mcellendorjffi 



Cerastus sp 



Limicolaria sp 



X 

 X 

 X 

 X 

 X 

 X 



X 

 X 



Recent. 



c s 



CD .JS 



« CD 'J C 



CD ~ 



ISO? 



5 



x 



X 

 X 



X 



■a« 



a 



S a 



> 







P 







od 



03 



.' 



NJ 



^C 



CD 







> 



ci 



>> 





on 



03 



« 







S 



O 



3 





C3 





X X 



X 

 X 



X 

 X 



In no other region of Africa has a similar molluscan fauna of 

 this age been found, the only Burdigalian beds known being those 

 of Moghara 1 and Wadi Faregh 3 in Egypt. They are, however, 

 differently constituted, having involved marine as well as estuarine 

 conditions in their formation, as proved by their fossil contents, 

 which consist of marine mollusca, echinoids, polyzoa, etc., a& 



1 C. W. Andrews, Geol. Mag. dec. 4, vol. vi (1899) pp. 481, 482. 



2 E. Stromer, Abhandl. Senckenb. Naturf. Gesellsck. vol. xxix (1907) p. 83. 



