INDIAN REGION. 225 



regions, we take into consideration the extent in wliicli an 

 exchange has taken place of the faunae originally peculiar to 

 each, we must estimate that obtaining between the fresh- 

 water fishes of the Europo-Asiatic and Indian regions as very- 

 slight indeed. 



2. There exists a great affinity between the Indian and 

 African regions ; seventeen out of the twenty-six families or 

 groups found in the former are represented by one or more 

 species in Africa, and many of the African species are not 

 even generically different from the Indian. As the majority 

 of these groups have many more representatives in India than 

 in Africa, we may reasonably assume that the African species 

 have been derived from the Indian stock ; but this is pro- 

 bably not the case with the Siluroid group of Clariina, which 

 with regard to species is nearly equally distributed between 

 the two regions, the African species being referable to three 

 genera (Clarias, Heterohranchus, Gymnallabcs, with the sub- 

 genus Channallahes), whilst the Indian species belong to two 

 genera only, viz. Clarias and Heterdbranchus. On the other 

 hand, the Indian region has derived from Africa one fresh- 

 water form only, viz. Etroplus, a member of the family of 

 Chromidcs, so well represented in tropical Africa and South 

 America. Mroplus inhabits Southern and Western India and 

 Ceylon, and has its nearest ally in a Madegasse Freshwater 

 fish, Faretroplus. Considering that other African Chromides 

 have acclimatised themselves at the present day in saline 

 water, we think it more probable that Etroplus should have 

 found its way to India through the ocean than over the 

 connecting land area; where, besides, it does not occur. 



3. A closer affinity between the Indian and Tropical 

 American regions than is indicated by the character of the 

 equatorial zone generally, does not exist. No genus of Fresh- 

 water fishes occurs in India and South America without bemg 

 found in the intermediate African region, with two exceptions. 



Q 



