FAUNA OF THE AFRICAN LAKES, 521 



Nyanza and Edward ISTyaiiza. Although Tangan3dka has certainly 

 received a considerable amount of attention, this circumstance 

 would not alone suffice to explain the relative richness of its 

 Ophidian fauna, which is the more remarkable in that two of the 

 species are endemic forms. It is hardly among the snakes that 

 types cliaracteristic of a lake would be expected, but they never- 

 tlieless afford an interesting parallel to the state of affairs which 

 is so constant and striking in most of the groups of typically 

 aquatic animals. 



Chelonia. 



Five species of aquatic tortoises come within the scope of this 

 survey*, of which four have been found in Tanganyika. 



1. Sternothcerus sinuatus. 



A form well known from Tanganyika and obtained by Stuhl- 

 mann in the Victoria Nyanza (192, p. 4). It has more recently 

 been reported from Nyasa (193, p. 583) and from Lake Albert 

 (180, p. 200), while it is widely distributed in South Africa and 

 in East Africa south of the equator. 



2. Sternothcerus derhianus. 



This species appears to be more especially West African, but 

 also occurs in Tanganyika. 



3. Sternothcerus nigricans. 



A specimen of this tortoise from Usumbura, Lake Tanganyika, 

 is referred to by Sternfeld in his report on the reptiles of the 

 Oerman Central Africa Expedition (180, p. 201). It is also 

 known from the region of Mozambique and from Madagascar. 



4. Pelomedusa gcdeatcc. 



This is likewise a widely distributed form, and is recorded by 

 Tornier (193, p. 583) both from Tanganyika and Victoria Nyanza. 

 It has again been reported from Victoria Nyanza by Sternfeld 

 (180, p. 201), and the British Museum also possesses a specimen 

 from that locality. The species does not seeiii to have been 

 mentioned hitherto from any of the other big lakes, although it 

 is well known fi'om Southern and Ti'Opical Africa and occurs 

 ■even as far north as the Sinaitic Peninsula. 



5'. Cyclodermafrenatum. 

 This well-known Zambezi type has been collected by Fiilleborn 



* Particulars of these Clieloiiiaus will be found in the British Museum Catalon-ue 

 (19)- 



Proc. Zool. Soc— 1920, No. XXXV. 35 



