130 MEMOIRS OF THE CARNEGIE MUSEUM. 



South Fork Holston River, Pactolus, Bluff City, and Emmett, Sullivan Co., Tennessee. 



Middle Fork Holston River, Chilhowie, Smyth Co., Virginia. 



North Fork Holston River, Rotherwood, Hawkins Co., Tennessee; Hilton, Scott Co., Virginia; Mendota, 



Wasliington Co., Virginia; Saltville, Smyth Co., Virginia. 

 Clinch River, Edgemoor and Offutt, Anderson Co.; Clinch River Station, Claiborne Co.; Oakman, 



Grainger Co., Tennessee; Speers Ferry and Clinchport, Scott Co., Virginia; St. Paul, Wise Co., 



Virginia; Fink and Cleveland, Russell Co., Virginia; Raven, Richland, and Cedar Bluff, Tazewell 



Co., Virginia. 

 Powell River, Combs, Claiborne Co., Tennessee; Dryden, Lee Co., Virginia. 



Distribution and Ecology in Pennsylvania (See fig. 12) : This species is widely 

 distributed in the headwaters of the Ohio in western Pennsylvania, and is found 

 in large rivers as well as in very small creeks, although it is distinctly more abundant 

 in the latter. There is hardly any small stream from which it is entirely absent, 

 but in the large rivers, although present, it is decidedly rare. 



The wide and general distribution of this species indicates that it is not very 

 particular as to station. It is found under a great variety of conditions, in riffles, 

 with a strong and variable current, in steady, stronger or weaker currents, and 

 even in rather quiet water and deep pools. It is found on every variety of bottom, 

 but prefers coarser or finer gravel, and more rarely is seen in sand and mud. It is 

 one of the few species, which advances far eastwards in the headwaters of the 

 Conemaugh and Allegheny drainages, but although it closely approaches the divide, 

 it has never been found in Pennsylvania to the east of it in the Atlantic-drainage. 



It has not been found in the only tributary of Lake Erie in our state, which 

 has shells (Conneaut Creek). 



General distribution: Type locality, Kentucky River (Rafinesque). 



This species has an enormous range. It is found practically all over the 

 Mississippi and Ohio-drainages, from western Pennsylvania throughout Ohio, 

 Indiana, Illinois, West Virginia, Kentucky, and Tennessee to northern Alabama. 

 In the upper Tennessee-drainage it goes by the Powell, Clinch, and Holston Rivers 

 into Virginia. In a southwesterly direction it extends to eastern Kansas, through 

 Arkansas to Oklahoma and northern Louisiana. 



Simpson cites it from Columbus, Lowndes Co., Mississippi, in the Tombigbee- 

 drainage, but this is the only place from which it has been recorded in the Alabama 

 system. 



Westward it does not seem to go beyond Iowa (abundant in the Wapsipinicon, 

 Volga, and Turkey Rivers, in northeastern Iowa, according to Geiser, 1910), but 

 in a northerly direction it has crossed over into the Hudson Bay-drainage in J\Iani- 

 toba, and possibly our locality in a northern tributary of Lake Superior (Kam- 

 inistiquia River), is connected with this region. 



