ICHTHYOLOGY. 25 



They extend from Eastern Afghanistan and Western Turkestan through Tibet, and the most 

 westerly portion of China, along the Himalayas to the hills in the Yunnan direction. 



Loaches (Ncmacheilus) are likewise generally distributed ; and it is remarkable, as I 

 have already observed, that all are scaleless. The same appears the rule in Western 

 Turkestan. 



The conclusion, I tliink, we may fairly arrive at, after examining the fishes of Yarkand 

 and the adjoining countries, is that we find a peculiar group of Carps (ScMzothoracince) which 

 has spread almost due east and west from the cold and elevated regions of Eastern Turkestan, 

 but of which the southern progress has been barred by the Himalayas. 



If we look to the south, we see, as it were, that a wave of tropical forms of fishes has, 

 at a prehistoric period, expanded over that portion of the globe where the Nicobars, Anda- 

 mans, and the most southern portions of the continent of Asia and the islands of the Malay 

 Archipelago now are, that this fish fauna has its northward progress arrested by some cause 

 at or near where the Himalayas now exist and mark the division between the fish-fauna of 

 India and that of Turkestan. 



