124 MEMOIRS OF THE CARNEGIE MUSEUM. 



Shenandoah River, Harpers Ferry, Jefferson Co., West Virginia. 

 South Fork Shenandoah River, Elkton, Rockingham Co., Virginia. 

 Rappahannock River, Remington, Fauquier Co., Virginia. 

 Rapidan River, Rapidan, Culpeper Co., Virginia. 

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



Kanaivha-drainage : 

 Pool of Kanawha River, Glen Ferris, Fayette Co., West Virginia. 

 Greenbrier River, Ronceverte, Greenbrier Co., West Virginia. 



New River, Hinton, Summers Co., West Virginia; Pearisburg, Giles Co., Virginia. 

 Reed Creek, Wytheville, Wythe Co., Virginia. 



Distribution and Ecology in Pennsylvania (See fig. 13) : According to the 

 records at hand, this species is very erratic in its distribution. It is found in all 

 three drainages on the Atlantic side, but it is evident that it avoids the large 

 rivers and prefers smaller streams. Its absence in the lists of Gabb (1861) ^^^ and 

 Schick (1895) is significant, although, as I have discovered, it is abundant in the 

 Schuylkill Canal at Manayunk. The specimens foimd by myself in larger rivers 

 generally were few, and often in small branches of the river. 



But even in small streams, it is not everywhere present. But generally, when 

 found, it turned up abundantly. Like the preceding species' (L. viridis), it is 

 averse to very strong current, and prefers more quiet parts, pools or eddies with 

 gravelly and sandy bottoms, and it also goes into canals, where it seems to flourish. 

 In the Susquehanna-drainage it goes far up into the headwaters, advancing west- 

 ward to Bedford, Cambria, and Indiana Cos. 



Outside of Pennsylvania, it is found under similar conditions, and is also 

 more abundant in smaller streams. In the Kanawha-drainage it descends to the 

 big pool above the Kanawha falls, where it lives in an environment resembling a 

 lake. 



« 



General distribution: Type locality, Frankstown Branch Juniata River, HoUi- 

 daysburg, Blair Co., Pennsylvania (Conrad). 



Simpson (1900) gives: "streams draining into the Atlantic from New York 

 south to North Carolina," and "Monroe Co., Michigan?". Of course, this latter 

 locality, doubted already by Walker (1898), is certainly incorrect. We possess 

 the largest number of locality records, outside of Pennsj'lvania, from the state of 

 New York (Marshall, 1895), where it is found in the drainages of the Susquehanna 

 and Hudson Rivers, and it goes westwards through the Mohawk into the Erie 

 Canal, reaching the Genesee River (See Baker, 18986). As has been said above, 

 in this region it overlaps L. viridis, but particulars as to the mutual relations of 

 these two species are absent. 



*' Gabb mentions it as a species, which might be found near Philadelphia. Conrad (1S36) reports a 

 single individual from the Schuylkill at Philadelphia. 



