310 the geography of mammals 



Deductions 



1. The Order Cetacea contains from eighty to ninety 

 known species, belonging to about forty-four genera and 

 four families. 



2. Cetaceans are found in all seas from the Equator to 

 within the Arctic and Antarctic Circles, and in some of 

 the larger rivers (the Ganges, Brahmaputra, Indus, and 

 Irawadi in the Old World, and the Amazon and La 

 Plata in the New). 



3. The species of Oceanic Cetaceans are mostly very 

 widely distributed, especially the Delphinidse, but in some 

 cases are local, some species being confined to the Arctic 

 and Antarctic Seas respectively, and some being peculiar 

 to the Pacific and to the North Atlantic. 



4. The Fluviatile Dolphins proper constitute a family 

 of themselves (Platanistida?) with a very singular distribu- 

 tion, one genus being restricted to the rivers of India, and 

 two others to those of South America. 



5. Besides the Platanistidse some of the Delphinidae are 

 found in rivers, such as Orcella fluminalis in the Irawadi, 

 and Sotalia tucuxi (with perhaps others of the same genus) 

 in the Amazon. 



6. None of the great lakes of any continent is known 

 to be inhabited by Cetaceans. 



