Occasional Papers of the Museum of Zoology 3 



on the right side ; right lateral margin slightly curved, left 

 lateral margin more convex ; the dorsal outline is flattened 

 above posteriorly and slightly curved anteriorly, the greatest 

 height being about in the centre of the shell, from which point 

 it slopes slightly towards the apex and more rapidly towards 

 the anterior margin, left lateral slope somewhat convex ; the 

 right lateral slope a little concave ; apex blunt, slightly de- 

 pressed, excentric. turned toward the right side, situated at 

 about the posterior fourth of the length and about halfway 

 between the median line and the right margin, radially striate ; 

 lines of growth rather strong and irregular, the anterior slope 

 is obsoletely radially rippled ; light horn color. 



Length 4.25 mm., width 2.75 mm., altitude i mm. 



Type Locality : Willow Brook, west of Harbert, Chickaming 

 Township, Berrien County, Michigan. 



Type Speciiitcn : Museum of Zoology, University of Mich- 

 igan, Xo. 13057. Cotypes in the collection of Bryant Walker. 



Tliis well marked species is the largest yet described from 

 the Northern States of the depressed group of Ferrissias. 

 While nearly as large as many examples of F. riz-nlnris and 

 F. tarda, the depressed form and apex readily differentiate it 

 from either. 



Numerous examples were collected from dead leaves and 

 sticks in a small pond above a dam in the brook, in 191 7, and 

 again in 1918 and 1922. In the same pond numerous other 

 species of freshwater snails were found, among them the small 

 Planorhis buclianensis Lea, Planorbi's ruhelhis Sterki, Lym- 

 iiaea columella Say, Lymnaea htimilis modicella Say, and 

 others. 



