356 ORTMANN— THE ALLEGHENIAN DIVIDE. [April 18, 



their distribution undoubtedly is correlated with the old Preglacial 

 drainage systems. Cambarus obscurus belongs to the old Monon- 

 gahela River, while C. propinquus sanborni indicates, in its present 

 distribution, the old Kanawha River. This theory has been fully 

 confirmed by my subsequent investigations, which have shown that 

 C. obscuras actually is the river-species of the Monongahela in West 

 Virginia, up to the headwaters of the Plateau stream West Fork 

 River, while to the south of this, in the little Kanawha, Big Kana- 

 wha, Guyandot, and in the corresponding part of the Ohio proper, 

 C. propinquus sanborni is found. This latter form probably is 

 also in the Big Sandy, and a few smaller streams to the west of this 

 in Kentucky, all belonging to the Old Kanawha of Preglacial times. 



The additional information was obtained that in Licking River 

 another species is found, C. rusticus. This means, that this river 

 had a more isolated position from the others in Preglacial times, 

 although belonging probably also to the old Erigan drainage. 



While thus the Najad fauna of the upper Ohio follows in its 

 distribution the modern features of this river, and while we are to 

 conclude, for this reason, that it is largely Postglacial, the crayfish 

 fauna indicates Preglacial conditions. And further, it seems that, 

 among the Pleuroceridce, we have both elements represented, but, 

 unfortunately, the natural affinities of this group are yet too obscure 

 to permit any final conclusions. 



Fact I., 2, (c). 



In the headwaters region of the mountain streams tributary to 

 the Monongahela and Kanawha, above the canyon, there is generally 

 a section, where these rivers are less rough, and run more quietly 

 in elevated, often broad valleys (compare profiles, PI. XIII. , fig. 2, pi. 

 XIV., fig. 1). As has been said, the fauna of these parts is chiefly 

 characterized by the absence of the common upper Ohio types. 

 Nevertheless we have a small number of forms here, which are 

 more or less characteristic. 



These forms are not uniformly present in all these rivers, and 

 their distribution may be tabulated as follows : 

 1. Monongahela drainage — 



