242 ON THE DISTRIBUTION OF FRESH-WATER FISHES 



Pomoxys sp., Umbra annulata, 



Ainbloplites rupestris, Esox, 2 sp., 



Hemioplites siraulans, Semotilus rhotheus, 

 Enneacanthus guttatus, " corporalis, 



Pomotis maculatus, Hypsilepis cornutus, 



Micropterus nigricans, v. afF., Catostomus communis, 



Haplochilus sp., Amiurus sp., 



Anguilla sp. 



From the above enumerations two points are evident : 



I. That species not generally distributed exist in waters on different sides of the 

 great water shed ; 



II. That the distribution of the species is not governed by the outlet of the rivers, 

 streams having similar discharges (Holston and Kanawha, Roanoke and Susque- 

 hanna) having less in common than others having differerent outlets (Kanawha and 

 Susquehanna, or James). 



In view of the first proposition, and the question of tlie origin of species, the 

 possibility of any original or subsequent mingling of the fresh waters suggests itself 

 as more probable than that of distinct origin in the different basins. 



Two questions arise : I. Has any destruction of the river faunte taken place since 

 the first elevation of the AUeghenies, when the same species were thrown into waters 

 flowing in opposite directions ? II. If so, has any means of communication existed, 

 at any time, but especially since the last submergence, by which the transfer of 

 species might occur ? 



The Allegheny region is believed to have been elevated at the close of the palaeozoic 

 ages, accompanied south and west of the Kanawha River by fiiulting on an immense 

 scale. At that time the valleys through which the larger of the present water 

 courses flow were established. Had the valleys been elevated above the ocean level 

 at that time, the sources of the streams would have been more widely removed than 

 now, at least as respects their habitability by fishes, since the mountains would have 

 been much more elevated than at present. As faults of eight thousand feet are 

 found, according to Rogers, in this region, the mountains themselves would have 

 risen beyond the snow line. The most elevated points of the same chain in this 

 region are now the Balsam Mountain, 5500 feet, and the Salt Pond Mountain, 5300 

 feet, indicating the great denudation which has followed. 



It is quite possible, indeed, that nothing more than the summits of the mountains 

 rose above the ocean for a considerable period subsequent to their first elevation, a,nd 

 that the enormous denudation which they have undergone was produced by the 

 Atlantic waves beating on them for a considerable period, as the continent slowly 



