448 FRANK COLLINS BAKER 



(about 20,000 specimens), indicating that this species is very rare 



in this marl deposit. Compared with the same species from the 



marl deposit in Urbana, Illinois, the Ohio shells are a trifle more 



depressed. 



Amnicolidae 



Amnicola walkeri Pilsbry. Most of the Amnicolas referred to 

 this species are quite typical, agreeing with Walker's figure in the 

 Nautilus (Vol. XIX, PI. V, Fig. 12). A few individuals have a 

 higher spire with strongly rounded whorls and a very deep suture, 

 i.e., scalariform. The largest specimen measures about 2.5 mm. 

 in length. This characteristic species is not common in this deposit, 

 only about fifty specimens being found in picking over a quart of 

 material. 



Amnicola lustrica Pilsbry. Variety. "Larger, more solid, 

 with the hp much thickened within" (Pilsbry). This Amnicola is, 

 equally with the following species, the most abundant species in the 

 deposit, nearly 40 per cent of the bulk of a quart being composed 

 of these two species of Amnicola. There is some variation in the 

 width of the shell and in the height of the spire, the whorls of which, 

 in some individuals, are quite round, with very deep sutures. 

 A single specimen is so decidedly scalariform as to render it quite 

 unrecognizable without its presence in the other material. Several 

 specimens of this variety measure 4.5 mm. in length. In most 

 individuals the inner lip (peristome) touches the parietal wall, but 

 in others it is separated by a deep suture and the edge of the aper- 

 ture is entirely separated from the body whorl. The same form of 

 lustrica occurs in post- Wisconsin deposits of the Chicago region. 



Amnicola winkleyi leightoni Baker. This Amnicola (described 

 in the Nautilus, Vol. XXXIII) is related to winkleyi Pilsbry, 

 described from Saco, Maine. It is uniformly wider, with somewhat 

 shouldered whorls. Together with Amnicola lustrica variety, it is 

 the most abundant species in this deposit. That a form related to 

 the Maine shell should be found so far removed from the original 

 locahty is surprising, particularly as it occurs in a deposit of late 

 Pleistocene age. The specimens have been examined by Dr. 

 Pilsbry, who indicated their relationship to his Maine species and 

 who agreed with the author as to their distinctness as a race 

 believed to be extinct. 



