224 FISHES. 



the present Dipnoi since or even before the beginning of the 

 tertiary epoch. 



Of the autochthont freshwater fishes of the Indian region, 

 some are still limited to it, viz., the Nandina, the Luciocepha- 

 lidcB (of which one species only exists in the Archipelago), of 

 Silnroids the Chacina and Bagariina, of Cypriaoids the Semi- 

 plotina and Homalopterina ; others very nearly so, like the 

 Labyrinthici, Opliiocephalidm, Mastacembelidce, of Siluroids 

 the Silurina, of Cyprinoids the Basborina and Danionina, and 

 SyrribranchidcB. 



The regions with which the Indian has least similarity 

 are the !N"orth American and Antarctic, as they are the most 

 distant. Its affinity to the other regions is of a very different 

 degree : — 



1. Its affinity to the Europo- Asiatic region is indicated 

 almost solely by three groups of Cyprinoids, viz., the Cypri- 

 nina, Ahramidina, and Cohitidina. The development of 

 these groups north and south of the Himalayas is due to 

 their common origin in the highlands of Asia ; but the forms 

 which descended into the tropical climate of the south are 

 now so distinct . from their northern brethren that most of 

 them are referred to distinct genera. The genera which are 

 still common to both regions are only the true Barbels 

 (Barlus), a genus which, of all Cyprinoids, has the largest 

 range over the old world, and of which some 160 species 

 have been described ; and, secondly, the Mountain Barbels 

 (Schieothorax, etc.), which, peculiar to the Alpine waters of 

 Central Asia, descend a short distance only towards the 

 tropical plains, but extend farther into rivers within the 

 northern temperate districts. The origin and the laws 

 of the distribution of the Cohitidina appear to have been 

 identical with those of Barbus, but they have not spread into 

 Africa. 



If, in determining the degree of affinity between two 



