GEOGRAPHICAL DISTRIBUTION 265 



single indigenous true freshwater fish, and the neigh- 

 bouring island of Borneo, with its hundreds of species 

 of Cat-fishes, Carps, Loaches, etc., is most striking. 



Having thus eliminated the Australian region, the 

 remainder of the world may be divided into five 

 regions of unequal value, corresponding roughly to 

 the continents of South America, North America, 

 Europe (with Northern Asia), Africa, and Asia south 

 of the central plateau. Of these, the Palaearctic 



FIG. 24. Distribution of Carp family (Cyprinidce). 



region, comprising Europe and Asia north of the 

 Himalayas, exhibits considerable affinity with the 

 Nearctic, or North American region, none at all with 

 South America, very little with Africa, but more 

 with tropical Asia; indeed, in Southern China the 

 Palaearctic and Indian regions merge into each other. 

 The Palaearctic region is characterized especially by 

 the presence of Perches (Percidce), Pikes (Esocidce], 

 Carps (CyprinidcB), Loaches (Cobitidce], etc., and by 

 the absence of several families peculiar either to 

 North America or to the tropical regions. Of the 



