256 



the same in l)oth areas, and there should Ite no marked differences. There are 

 none. But mingling with the Western fauna of the Upper Wabash were found 

 large numbers of the Eastern strepomatid shell. Gonioba-ns livescens, a form which 

 is abundant from New York throughout Northern Ohio and along the Great 

 Lakes. Near Huntington, on the Wabash, this shell was the most abundant 

 strepomatid found. The same facts were true of the St. Mary's and the Maumee, 

 thougli the greatest numbers were found in the former stream, clinging to the 

 rocks along the banks, in the heart of the city of Fort Wayne. Associa'ted with 

 them were large numbers of Pleurocera subulare, a form abundant in the East, but 

 also of wide Western distribution, and an undetermined pleuroceroid mollusk of 

 Western affinities. It closely resembles Pleurocera lewidi, but of this determina- 

 tion I am yet uncertain. 



It is important to note, in this connection, that the headwaters of the Aboite 

 River, or its east fork, approach to within three miles of the St. Mary's at Fort 

 Wayne, and that the divide at that locality is hardly perceptible. Moreover, the 

 Wabash tSi; Erie Canal has long established water communication between the two 

 basins — ^probably long enough to establish interchange of faunas, especially in the 

 case of the univalves, which are far more migratory in their habits than the 

 Unionid;e. This is the case in the Erie Canal in New York, by means of which 

 the advent of the Western fauna into Eastern waters may be almost chronolog- 

 ically traced. To offset this possible explanation is the fact that the species seem 

 to be well established, and occur, many of them, in great numbers in the Maumee 

 Basin. But, whatever the explanation, the species appear in the two basins, and 

 in them both there is a commingling of the two faunas, with but few Western rep- 

 resentatives of the Eastern fauna. The Eastern representatives in the Western 

 fauna greatly outnuml)er, both in species and individuals, the Eastern fauna in 

 the Western Basin. 



The suggestion of the relation of this distribution to glaciation and its physi- 

 ographic results has before occurred to the writer, though in another connection. 

 As long ago as ISSfi, in discussing certain anomalies in the distribution of Ohio 

 River forms of Union id<i in the State of Kansas, attention was directed to this 

 problem in the following language : "Considerable data have accumulated in the 

 hands of the writer which seem to imply the necessity of correlating this peculiar 

 distribution with certain facts in glacial geology, but those data will not warrant 

 the statement that such correlation exists. Attention is directed to this problem 

 in the hope that other observers may use their opportunities and supply all the in- 



