I9I3-] ORTMANN— THE ALLEGHENIAN DIVIDE. 335 



of the propinquus group (obscurus and propinquus sanborni) have 

 the same peculiarity as the Najades, in going up, in the rivers, only 

 to the falls line in the mountain streams of West Virginia and south- 

 ern Pennsylvania, while in the upper Allegheny they go up nearly 

 to the sources. The fact that in the Kiskiminetas-Conemaugh they 

 do not follow the Najades into Somerset Co., and that thus this river 

 resembles the southern ones ; and that then again the upper Loyal- 

 hanna conforms with the northern streams, is not very astonishing, 

 for the Kiskiminetas system, being geographically intermediate, 

 should also be expected to form faunistically a transition. 



These crayfishes, however, differ from the Najades, in present- 

 ing a uniformity of the upper Ohio fauna only in so far as they are 

 systematically closely allied, belonging all into the same natural 

 group. But specifically they are quite sharply distinct, and thus 

 indicate, in their distribution, three faunistically different sections: 

 the upper Ohio is characterized by C. obscurus, farther down C. pro- 

 pinquus sanborni takes its place, and finally, beginning with Licking 

 River, C. rusticus turns up, and this species has a representative also 

 in the upper Tennessee, C. spinosus. 



These conditions are important for the history of the crayfish 

 fauna of the Ohio basin, and suggest, as I believe, that the Najad 

 and the crayfish population of this system was not entirely subject 

 to the same laws. 



Cambarus bartoni (Fabr.). This is not a river species, but a 

 species of the small and smallest creeks, going up to the very springs. 

 It is found everywhere on the western side of the mountains, for 

 instance, Blackwater River and Shaver's Fork, small runs tributary 

 to Buckhannon River, upper New River drainage (Reed Creek), 

 and small runs tributary to Clinch River. It is also on the Atlantic 

 side (see below). 



Cambarus longulus Gir. Is found, on the western side, only in 

 the upper Kanawha drainage, Greenbrier and New Rivers, and also 

 in the upper Tennessee drainage, Holston and Clinch. It is also on 

 the Atlantic side (see below). 



PROC. AMER. PHIL. SOC., LH. 2 IO D, PRINTED JULY II, I913. 



