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 ( Nemacheilus ) 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 think, we may fairly arrive at, after examining the fishes of Yarkand 
and the adjoining countries, is that we find a peculiar group of Carps (S cliizothoracince) which 
has spread almost due east and west from the cold and elevated regions of Eastern Turkestan, 
hut 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- 
nians, 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 w r here the Himalayas now exist and mark the division between the fish-fauna of 
India and that of Turkestan. 
