DISPERSION OF FRESH-WATER FISHES. 121 



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 faunae 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 Ameiurus nebulosus Le Sueur. 



