I9I3-] ORTMANN— THE ALLEGHENIAN DIVIDE. 329 



This is a fact which should be emphasized, for in the head- 

 waters of the Monongahela, Anculosa dilatata turns up. This is 

 found in the lower part of the Cheat at Cheat Haven, Fayette Co., 

 Pa., and goes up through the canyon into the headwaters (Shavers 

 Fork, Parsons, Tucker Co., W. Va.) ; it is also in Tygart Valley 

 River, at Elkins, Randolph Co., W. Va., and even in the plateau 

 stream, West Fork River, at Lynch Mines, Harrison Co., W. Va. 



No Anculosas are found in the rest of the upper Ohio drainage 

 in western Pennsylvania. 



Farther south in West Virginia our knowledge probably is frag- 

 mentary. In the Kanawha drainage, no Pleuroceridce are known to 

 me, except Pleurocera validum Anth. in Elk River ; and New River 

 and Greenbrier rivers, at least from Hinton upward, contain Ancu- 

 losa dilatata (Conr.). The latter is exceedingly abundant in this 

 region. 



In the Big Sandy, at Prestonsburg, Floyd Co., Ky., I collected 

 Pleurocera unciale Hald., a species which is also found in Clinch 

 River. Licking River at Farmer, Rowan Co., Ky., has Pleurocera 

 cylindraceum Lea. 



It appears that there is a certain correlation in the distribution 

 of the Pleuroceridce and the Najades of the upper Ohio drainage, at 

 least as far as it concerns the genera Pleurocera and Goniobasis. It 

 is well known that the greatest variety of forms is found in the lower 

 Ohio and its tributaries, and it is suggested that this fauna has 

 migrated upstream, and that there is a general decrease in the num- 

 ber of species in an upstream direction. But the different tributaries 

 of the upper Ohio seem to have received or have developed different 

 species. In addition, most of the species do not go very far into the 

 headwaters, and the smaller streams generally do not contain Pleuro- 

 ceridce, or only rarely so. 6 



One very remarkable fact is to be noted. In the headwaters of 

 the Monongahela, excluding the Youghiogheny, and also in the 

 headwaters of the Kanawha (New and Greenbrier rivers), Anculosa 



6 This, however, is different in the Beaver drainage, where species of 

 Goniobasis are found in small creeks. But the characteristic species', G. lives- 

 cens, probably did not come up the Ohio, but came " across country " from 

 the West. 



