6o FRANK COLLINS BAKER 



and the species probably has a wide distribution in Pleistocene 

 deposits, from which it has been listed as limosa. 



Amnicola walkeri Pilsbry. A common species in this deposit. 

 Also widely distributed. 



Amnicola lustrica gelida Baker. This variety of Amnicola 

 lustrica was recorded as lustrica variety in a previous paper on 

 Ohio glacial mollusks (Baker, 1920a, p. 448). It occurs abun- 

 dantly in the Gundy County deposits, at Chicago, in other parts of 

 Illinois, in Wisconsin, and in Michigan. It is constantly separable 

 from typical lustrica and should have a name to distinguish it 

 (see Baker, 1921, p. 22). It is probably peculiar to Pleistocene 

 time. 



Valvata tricarinata (Say). Both Recent and Pleistocene 

 carinate Valvatae show a large amount of variation in the degree 

 of carination. Most of these variations have been named and 

 but one possible combination seems unrecognized (supracarinata) , 

 and this has been characterized from specimens in the Grundy 

 County deposit (Baker, 1921, p. 24). Of these possible variations, 

 seven in all, five occur in the deposit under discussion. These are: 



Valvata tricarinata (Say), common. 



Vahata tricarinata perconfusa Walker, abundant. 



Valvata tricarinata infracarinata Vanatta, rare, two specimens observed. 



Valvata tricarinata supracarinata Baker, rare, four specimens observed. 



Valvata tricarinata simplex Gould, rare, one specimen observed. 



Physa anatina Lea. A common Physa in this deposit appears 

 to be Lea's species, although the spire is not as high as in normal 

 anatina. 



Physa walkeri Crandall. Common, associated with anatina. 

 Apparently typical. Both species are widely distributed in Pleisto- 

 cene deposits. 



Planorbis campanulatus Say. Rare, but two specimens observed. 



Planorbis antrosus Conrad. 



Planorbis antrosus striatus Baker. Both antrosus and its 

 variety striatus occurred commonly, in about equal numbers. A 

 very common species in Pleistocene deposits. 



Planorbis deflectus Say. Not common. Typical of the species 

 as found Recent. 



