312 ORTMANN— THE ALLEGHENIAN DIVIDE. [April 18, 



tata, Alasmidonta marginata, Strophitus edentulus, Lampsilis ovata 

 ventricosa, Lampsilis multiradiata) . All others (about 20) are not 

 found in the upper Ohio drainage ; some have representative forms 

 there (Fusconaia bursa-pastoris, Quadrula cylindrica strigillata, 

 Eurynia nebulosa, Truncilla capsaeformis) ; but others are types, 

 which are not at all represented there (Pleurobema fassinans, Alas- 

 midonta minor and fabula, the genus Medionidus, Eurynia perpur- 

 purea and vanuxemensis, Truncilla haysiana are the most important 

 ones). 



It should be noted especially that the New River species, Elliptio 

 dilatatus and Alasmidonta marginata, which are found in the Ten- 

 nessee drainage, are not represented by identical forms. Elliptio 

 dilatatus of upper New River is a dwarf race, while the Clinch type 

 is large and normal. The Clinch and Holston type of Alasmidonta 

 marginata is peculiar by its extremely bright color markings. 



The contrast between these rivers is thus clearly established, and 

 becomes even more striking, when we consider the fact that in gen- 

 eral physiographic characters these rivers are very similar to each 

 other, and further, that the Holston and Clinch, where I collected 

 in them, are much smaller, mere creeks, compared, for instance, with 

 New River at Pearisburg. 



Summary of Facts Concerning the Western Fauna. 



To express it in a few words, the chief features of the western 

 fauna are: a uniform fauna goes from Licking River up through 

 the whole upper Ohio drainage into the headwaters of the Allegheny, 

 but in the mountain streams tributary to the Monongahela and 

 Kanawha a sudden depauperation is observed and farther above 

 very few species are present. The fauna of the upper Tennessee 

 is related to the Ohio fauna, but has many peculiar elements. As 

 a whole, the Ohio fauna is to be regarded as a somewhat depau- 

 perated Tennessee fauna ; this is not so evident from the lists given 

 above, but is a well-known fact, for which we do not need to furnish 

 here particular proof. 



