Barriers to Dispersion of River Fishes 3 1 1 



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 Alleghanies forms a barrier of im- 

 portance separating the rich fish fauna of the Tennessee and 

 Ohio basins from the scantier faunse of the Atlantic streams. 

 Yet this barrier is crossed by many more species than is the 

 case with either the Rocky Alountains 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 Rocky Mountains, seems 

 not to be an element of any importance in this connection. Of 

 the fish which cross this chain, the most prominent is the brook 

 trout,* which is found in all suitable waters from Hudson's 

 Bay to the head of the Chattahoochee. 



Upland Fishes. — A few other species are locally found in 

 the head waters of certain streams on opposite sides of the range. 

 An example of this is the little red " fallfish,"t found only in the 

 mountain tributaries of the Savannah and the Tennessee. We 

 may suppose the same agencies to have assisted these species 

 that we have imagined in the case of the Rocky Mountain trout, 

 and such agencies were doubtless more operative in the times 

 immediately following the glacial epoch than they are now. 

 Prof. Cope calls attention also to the numerous caverns existing 

 in these mountains as a sufficient medium for the transfer of 

 many species. I doubt whether the main chains of the Blue 

 Ridge or the Great Smoky can be crossed in that way, though 

 such channels are not rare in the subcarboniferous limestones 

 of the Cumberland range. In the brooks at the head waters of 

 the Roanoke River about Alleghany Springs in Virginia, fishes 

 of the Tennessee Basin are found, instead of those characteristic 



* Salvelinus fontinalis. 



t Notropis rubricroceus Cope. 



