302 ORTMANN— THE ALLEGHENIAN DIVIDE. [April 18, 



observed at any point. In the uppermost headwaters there is yet a 

 comparatively rich fauna of together 14 species. 



We shall see that in other parts of the western drainage this con- 

 dition is not found, and our rather detailed account of the Allegheny 

 fauna has been given with the chief purpose of bringing out the 

 above fact. 



IV. MONONGAHELA RiVER AND TRIBUTARIES. 



We have seen above (list no. 3) that the Monongahela just above 

 Pittsburgh had surely 28 species, but possibly 2)3- Farther up no 

 Na jades are known and the fauna is destroyed, for the water is 

 everywhere badly polluted. But above Clarksburg, Harrison Co., 

 W. Va., conditions are good again in West Fork River. This is a 

 Plateau stream, not rough, but rather sluggish, and the proper en- 

 vironment for shell-life seems to be present. The Carnegie Museum 

 possesses material collected by the writer at Lynch Mines, Harrison 

 Co., at Lightburn and Weston, Lewis Co., and some additional forms 

 collected by J. P. Graham at West Milford, Harrison Co., W. Va. 

 This gives us a good, and, as I believe, a rather complete idea of 

 this fauna. 



In the following list those forms found at the uppermost point 

 in this river (Weston) are marked with a *. (None is peculiar to 

 this locality.) 



List No. 10. 



I. Fusconaia subrotunda (Lea) 

 *2. Crenodonta plicata undulata (Barn.) 



3. Quadrula tuberculata (Barn.) 



4. Quadrula metanevra zvardi (Lea) 



5. Quadrula cylindrica (Say) 



6. Rotundaria tuberculata (Raf.) 



*7. Pleurohema obliquum coccineum (Conr.) 

 *8. Pleurobema clava (Lam.) 

 *9. Elliptio dilatatus (Raf.) 

 *io. Symphynota costata (Raf.) 

 II. Hemilastena ambigua (Say) 



