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■of fishes. We can also see how it might be that certain mountain 

 fishes should be so transferred while the fishes of the upland 

 waters may be left behind. In some such way as this we may 

 imagine the trout and the whitefish to have attained their pres- 

 ent wide range in the Rocky Mountain region ; and in similar 

 manner perhaps the Eastern brook trout {Salvelimis fontinalis 

 Mitchill) and some other mountain species [Notropis rubricroceiis 

 Cope ; RJiinichthys atronasus Mitchill, etc.) may have been car- 

 ried across the AUeghanies. 



The Sierra Nevada constitutes also a very important 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 unfavor- 

 able for the growth of eastern fishes is shown by the fact of the 

 rapid spread of the common eastern catfish {Anieiiiriis nebii- 

 losus Le Sueur) or horned pout, when transported from the 

 Schuylkill to the Sacramento. This fish is now one of the im- 

 portant 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 temperament as in habits. 



The mountain mass of Mount Shasta is, as already 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 AUeghanies forms a barrier of im- 

 portance separating the rich fish-fauna of the Tennessee and 

 Ohio basins from the scantier faunae of the Atlantic streams. 

 Yet this barrier 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 broken, 

 — as in New York, in Pennsylvania, and in Georgia there are 

 several streams which pass through it or around it. The 

 much greater age of the Alleghany chain, as compared with the 



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