204 MEMOIRS OF THE CARNEGIE MUSEUM. 



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

 South Fork Powell River, Big Stone Gap, Wise Co., Virginia. 



Mississippi River and westward: 

 Mississippi River, Muscatine, Muscatine Co., Iowa (Hartman collection). 

 Meramec River, IMeramec Highlands, St. Louis Co., Missouri (N. M. Grier). 

 Hinkston Creek, Columbia, Boone Co., Missouri (D. K. Greger). 

 James River, Galena, Stone Co., Missouri (A. A. Hinkley). 

 White River, Hollister, Taney Co., Missouri (W. I. Utterback); Cotter and Norfolk, Baxter Co., Arkansas 



(A. A. Hinkley). 

 Black River, Black Rock, Lawrence Co., Arkansas (H. E. Wheeler). 

 Saline River, Benton, Saline Co., Arkansas (H. E. Wheeler). 

 Ouacliita River, Arkadelphia, Clark Co., Arkansas (H. E. Wheeler). 

 Lawrence, Douglas Co., Kansas (R. L. Moodie). 

 Fourteen Mile Creek, Fort Gibson, Muskogee Co., Oklahoma (F. B. Isely). 



Atlantic-drainage : 

 Delaware-Raritan Canal, Princeton, Mercer Co., New Jersey. 

 Potomac River, Hancock, Washington Co., Maryland. 

 South Branch Potomac River, Romney, Hampshire Co., West Virginia. 

 North Fork Shenandoah River, Broadway, Rockingham Co., Virginia. 

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

 South River, Waynesboro, Augusta Co., Virginia. 

 Rappahannock River, Remington, Fauquier Co., Virginia. 

 Rapidan River, Rapidan, Culpeper Co., V'irginia. 

 Mountain Run, Culpeper, Culpeper Co., Virginia. 

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

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

 Roanoke River, Salem, Roanoke Co., Virginia. 

 Mason Creek, Salem, Roanoke Co., Virginia. 



Distribution and Ecology in Pennsylvania (See figs. 20 & 21): This is the 

 only species of Naiad whose range covers the whole of the state of Pennsylvania, 

 the divide of the Allegheny Mountains havmg no influence whatever upon it. 

 The forms found on either side of the divide do not differ at all, and go far up into 

 the headwaters, so that there is practical continuity of distribution across the 

 divide. There is no doubt that this distribution is to be accounted for by an 

 actual crossing over from the western to the eastern slope, and probably this has 

 been effected by stream piracy. This has been discussed elsewhere (Ortmann, 

 1913a, pp. 367-369). 



Strophitus edentulus also is extremel.y common aU over the state, although it 

 is distinctly averse to large rivers. Rhoads reports it from the Ohio below Pitts- 

 burgh, but I have never found it there. Above Pittsburgh it appears in the Alle- 

 gheny, but is decidedly scarce in Allegheny and Armstrong Cos., and the specimens 



