180 MEMOIRS OF THE CARNEGIE MUSEUM. 



South River, Waynesboro, Augusta Co., Virginia. • 



Rappahannock River and Marsh Run, Remington, Fauquier Co., Virginia. 

 North River, Buena Vista and Lexington, Rockbridge Co., Virginia. 

 Calf Pasture River, Goshen, Rockbridge Co., Virginia. 



Distribution and Ecology in Pennsylvania (See fig. 17) : A common species in 

 the Atlantic-drainage in Pennsylvania; but it is quite evident that it avoids the 

 larger rivers, and prefers the smaller streams, where it becomes locally very abun- 

 dant, going far up towards the headwaters, as is best seen in the upper Juniata and 

 the tributaries of the West Branch of the Susquehanna in Cambria Co. Here it 

 closely approaches the divide, but in no instance has it been found west of the 

 divide. 



It does not seem to favor riffles and very rough water, but is found chiefly in 

 more quiet parts, but with some current, for instance, above riffles, where a steady 

 flow of water prevails. It does not like slackwater, but occasionally it is found 

 in ponds and canals; and it has been reported from several lakes in New York. 

 It also likes mill-races, if the current is not too rapid. It lives mostly in a mixture 

 of coarser or finer gravel with sand and mud; but I have taken it also in eddies 

 with slow current embedded in the mud deposited between larger stones. 



General distribution: Type locality, Delaware River, near Philadelphia (Say). 



According to Simpson (1900), this species extends from the "Lower St. Law- 

 rence-drainage southward to North Carolina." Its presence in the lower St. 

 Lawrence (below Lake Ontario) is well established (Bell, 1859; Whiteaves, 1863; 

 Marshall, 1895). In New York state it is found in the St. Lawrence-drainage, 

 as in Lake Champlain (De Kaj", 1843), Seneca and Crooked Lakes (Dewej^, 1856); 

 and in Onondago Co. (Marshall). It is more abundant stiU in the drainage of 

 the Mohawk and Hudson Rivers, and of the upper Susquehanna (Chenango, 

 Canisteo, Conhocton, and Tioga Rivers) (See De Kay, 1843; Lewis, 1860; Marshall, 

 1895). 



It has been reported from Maine (Lermond, 1909; Nylander, 1914), from 

 Keene, Cheshire Co., New Hampshire (Walker & Coolidge, 1908), and is rather 

 common in Vermont (Adams, 1842), Massachusetts (Gould-Binney, 1870), Rhode 

 Island (Carpenter, 1890), Connecticut (Linsley, 1845; Perkins, 1869) (See also 

 Johnson, 1915, p. 26). 



South of Pennsylvania it has been previously' recorded from Sideling Creek, 

 AUegany Co., Maryland (Pilsbry, 1894), and from Raleigh, Wake Co., North 

 Carolina (Marshall, 1895), but other exact localities are not known to me. How- 

 ever that it exists in the Potomac, Rappahannock, and uj^per James drainages 

 is shown by the material collected by myself for the Carnegie Museum. 



