312 ORTMAXX— THE ALLEGHEXIAX DIVIDE. [April i8, 



tata, Alasmidonta marginata, Strophitns edentuliis, Lantpsilis ovata 

 ventricosa, Lauipsilis ninltiradiata). All others (about 20) are not 

 found in the upper Ohio drainage ; some have representative forms 

 there (Fusconaia biirsa^pastoris, QnadrnJa cylindrica strigillata, 

 Eitrynia nehulosa, Tnincilla capsaeformis) ; but others are t^-pes, 

 which are not at all represented there (Pleurobenia fassinaiis, Alas- 

 midonta uiinor and fabnia, the genus Medioiiidiis, Eurynia perpnr- 

 piirea and vanuxcniensis, Tnincilla haysiaiia are the most important 

 ones). 



It should be noted especially that the Xew 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 Xew 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 

 Xew River at Pearisburg. 



Summary of Facts Coxcerxixg the Western Faux a. 



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

 fauna are: a unifonn 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 JMonongahela and 

 Kanawha a sudden- depauperation is observed and farther above 

 very feiv 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. 



