236 Quarterly Joiunal of CojtcJioIogy. 



BiiUia is represented at Zanzibar by one or two scarce spec'es ; 

 at Natal and Algoa Bay there are 10 or 12 species and individuals 

 are numerous. 



The genus Cyprcea furnishes more than 30 species on the tropical 



East Coast, and with few exceptions each species is individually 

 numerous. Below Natal the species are few, principally belonging 

 to subgenera, and individuals are rare. Strombus with 8 species at 

 Zanzibar is represented at Natal by a solitary straggler, {S.floridus, 

 Lam.) Typical species oi Nassa prevail along the East Coast; 

 to the South they are replaced by species belonging to the sub- 

 genera Dcsmoulea, Cyclcnassa, c^c. 



Fissunila (with the subgenera) contains 15 or more S. African 

 species. I found but one in E. Africa. 



The Troclii, 3c in number, cover the rocks at Cape Town and 

 Algoa Bay in vast numbers from high water mark downwards. At 

 Zanzibar a few species are sparingly found, lurking under stones at 

 low water only. 



Ricinula and CeritJiium are well developed genera in the tropics, 

 fairly represented at Natal and all but absent at the Cape. Flanaxis, 

 Oliva, Nerita, Parmophorus and other genera do not extend below 

 Natal. Some genera are pretty evenly divided, having a common 

 meeting ground at Natal and Inhambane, e.g., Littorina, Cassis, 

 Q^c. In walking over a coral reef at Zanzibar, the shells that strike 

 the eye are Strombus, Cyprcea, Tiirbinella, CeritJiium and Ricinula, 

 whilst between tide marks at Algoa Bay or Cape Town, one notices 

 the great abundance of Patella, Siphonaria, Trochus, Cominclla 

 and Bullia. On such a large extent of coast there are necessarily 

 considerable local differences between Zanzibar and Mozambique, 

 however, they are few or none. The moUuscan fauna of Inham- 

 bane is peculiar, inasmuch as certain widely distributed tropical 

 species are found there which are absent or scarce higher up the 



