OrTMANN: NAIADES OF THE GREEN RIVER DRAINAGE. 187 
The two systems, at some time in the past, were separated, the Ohioan 
(or whatever was its master-stream) having no connection with the 
Cumberlandian River (Cumberland + Tennessee). Later on, how- 
ever, the present conditions were established, very probably by the 
deflection of the Tennessee and Cumberland toward the North and 
toward the Ohio, and there is no question, that the northward flowing 
parts of these rivers are of rather modern origin. This union with the 
Ohio must have brought about a partial mingling of the old faunas, 
and we have introduced above evidence for the invasion of Ohioan 
types into the lower Cumberland and Tennessee (Ortmann, 1925, 
p. 365). But, of course, an exchange should have gone on also in the 
opposite direction, Cumberlandian elements invading the lower Ohio. 
I have alluded to this previously (Ortmann, 1925, p. 364, footnote; 
p. 370), and instances of this will be found among those forms, which 
are uniformly distributed over the Interior Basin and the Cumberland- 
Tennessee drainage. But the distribution of these forms in the 
Interior Basin must be studied more closely, before we can point 
them out. These forms indicate the present unity of these river 
systems, and have largely obliterated the past condition of faunal 
separation, prevailing at an earlier period; yet distinct evidence of 
the latter still remains, as we have seen above. 
There is yet in Kentucky the Salt River system, between the Green 
and Kentucky Rivers. A few scattered records from it are at hand, 
but no intensive collecting has ever been done there. However, it is 
to be expected, that this drainage also has a fauna similar to those of 
the Kentucky and Green Rivers, that is to say, an Ohioan fauna, 
without typical Cumberlandian elements. 
BIBLIOGRAPHY. 
Catt, R. E. A Geographical Catalogue of the Unionide of the 
Mississippi Valley (Bull. Des Moines Acad. Sci., I, 1885, pp. 5-57). 
DANGLADE, E. The Kentucky River and its Mussel Resources (Bur. 
Fisher.; Doc. No. 934. 1922, pp. 1-8). 
OrTMANN, A. E. The Alleghenian Divide and its Influence upon the 
Freshwater Fauna (Proc. Amer. Philos. Soc., LIT, 1913, pp. 289- 
390). 
