292 ORTMANN— CORRELATION OF SHAPE AND 



The true metanevra is restricted mainly to larger rivers. But 

 occasionally it goes into smaller rivers, but hardly ever into the 

 headwaters. It has been reported repeatedly from rather small 

 streams, but then it was generally represented by the var. wardi. 

 The original localities of the latter are Walhond'mg River, Ohio 

 (tributary to Tuscarawas); Wapsipinicon' River (Wassepinicon), 

 Iowa; and Coal River, Logan Co., Va. (Coal River is now in 

 Kanawha and Boone Cos., W. Va.). Three specimens from the 

 latter locality were in the Hartman collection, and are now in the 

 Carnegie Museum. 



Sterki^'^ reports zvardi from Sugar Creek, another tributary of 

 Tuscarawas River. 



Aside from the types of zvardi from Coal River, the Carnegie 

 Museum possesses this form from the Ohio, Monongahela and Alle- 

 gheny Rivers in the vicinity of Pittsburgh. But these specimens 

 are not very typical, are rare, and intergrade with the normal 

 metanevra. They are found, however, at and near the upstream 

 limit of the distribution of the species. A rather good specimen of 

 zvardi comes from the Little Kanazvha River at Burnsville. This 

 again is a smaller stream. 



Thus the tendency is observed, when the species enters smaller 

 streams, to develop a compressed variety. But, in addition, this 

 variety inclines to obliterate a peculiar sculpture, very character- 

 istic for the main species, that of large knobs upon the surface of 

 the shell. This should be kept in mind. 



QuADRULA CYLiNDRiCA (Say). Simpson, '14, p. 832. 



This widely distributed species ordinarily is strongly nodulous, 

 with great knobs upon the posterior ridge, and the shell is generally 

 much swollen. Its characters are rather uniform over the range. 



However in the headwaters of the Ohio River, in Ohio and 

 Pennsylvania, and in the upper Tennessee-region, two peculiar small- 

 stream-races have developed. In the Tuscarawas River, in Beaver 

 River, and French Creek, there is a remarkably compressed form, 

 which, in addition, is practically smooth, having lost not only the 



^^ Proc. Ohio Acad. Sci., 4, 1907. 



