470 MICHIGAN SURVEY, 1905. 



Section STENOTREMA Rafinesque. 



Shell small, compact, imperforate or umbilicate; sub-globose, globosely 

 depressed or lens-shaped, the periphery varying from rounded to acutely 

 keeled, surface dull, smooth, generally hirsute. Whorls, 5-6 closely re- 

 volving, the last suddenly deflexed in front. Aperture basal, narrow, ob- 

 structed by an oblique blade-like parietal tooth, parallel to the reflexed 

 basal lip, the latter often notched in the middle. Last whorl generally 

 having in its last fourth, a shorty transverse, internal partition on the axis. 



KEY TO THE SPECIES 0F_ STENOTREMA. 



I. Lip notched hirsuta. 



11. Lip without notch. 



a. Base narrowly excavated, imperforate or narrowly umbilicate, hirsute, 



diameter 1 1 mm fraterna. 



aa. Basal excavation and umbilicus wider, smooth, depressed^ diameter 

 9 mm monodon. 



POLYQYRA HIRSUTA (Say) 



Shell imperforate, sub-globose; brownish or chestnut, thickly 



hirsute; spire convex, elevated; whorls 5, rounded; suture distinct; 



aperture contracted, very narrow, almost closed by an elongated, 



lamelliform tooth on the parietal wall, extending from the center 



Fig. 22. of the base into the edge of the aperture; peristome narrow, 



(Binney.) Very much depressed and reflected against the outer whorl, with 



a deep notch near the centre; base convex. 



Alt. 4§, greater diam. 7^,. lesser 7 mm. 



Helix hirsuta, Say, Jour. A. N. S. P., I., 17, (1817). 



Stenotrema hirsutum, W. G. Binnev, Man. Am. Land Shells, 278, fig. 295,, 



(1885). 

 Helix hirsuta, Sager, Doc. H. Rep. Mich., 1839, 420, separate, 14. 



, Miles, Rep. Geol. Surv. Mich., 235, (1861). 



Stenotrema , Currier, Shell-bearing Moll. Mich., 5, (1868). 



, DeCamp, Shell-bearing Moll. Mich., 7, (1881). 



Polygyra , Walker, Rev. Moll. Fauna Mich., 17, (1894). 



Common where found, but apparently local in its distribution. Macomb, 

 Wayne, Washtenaw, and Monroe, in the southeastern part of the state, 

 and Branch, Berrien, Kent, and Muskegon, in the western, are the only 

 counties thus far to be credited with it. It probably has a general distri- 

 bution south of the Saginaw-Grand Valley. 



^f^ POLYGYRA FRATERNA (Say) 



Shell narrowly umbilicated or imperforate, globose, de- 

 pressed, reddish horn-colored, minutely hirsute; whorls 5^, 

 (the upper ones flattened, the two last convex, the last con- 

 stricted behind the peristome; aperture widely l^inar,. with a 

 rlTS. p. fraterna. l^i'^^elli^oi'^ tooth ou the parietal wall; peristome narrow, 

 (Binney.) reflected, base convex, narrowly excavated. 

 Alt. 6, greater diam. 11, lesser 10 mm. 

 Helix fraterna, Say, Long's Exped. II, 257, pi. XV., fig. 3, (1824). 



