DISPERSION OF FRESH-WATER FISHES. [21 
The Sierra Nevada constitutes also a very im- 
portant barrier to the diffusion of species. This is, 
however, broken by the passage of the Columbia 
River, and many species thus find their way across 
it. That the waters to the west of it are not un- 
favorable for the growth of eastern fishes is shown 
by the fact of the rapid spread of the Common 
Eastern Cat-fish,! or Horned Pout, when trans- 
ported from the Schuylkill to the Sacramento. 
This fish is now one of the important food-fishes 
of the San Francisco markets. It has become, in 
fact, an especial favorite with the Chinaman, — 
himself also an immigrant, and presenting certain 
analogies with the fish in question, as well in tem- 
perament as in habits. 
The mountain mass of Mount Shasta is, as al- 
ready stated, a considerable barrier to the range 
of fishes, though a number of species find their 
way around it through the sea. The lower and 
irregular ridges of the Coast Range are of small 
importance in this regard, as the streams of their 
east slope reach the sea on the west through San 
Francisco Bay. Yet the San Joaquin contains a 
few species, not yet recorded from the smaller rivers 
of southwestern California. 
The main chain of the Alleghanies forms a bar- 
rier of importance separating the rich fish-fauna 
of the Tennessee and Ohio basins from the scan- 
tier faunze of the Atlantic streams. Yet this bar- 
rier is crossed by many more species than is the 
case with either the Rocky Mountains or the Sierra 
Nevada. It is lower, narrower, and much more 
1 Amerurus nebulosus Le Sueur. 
