58 POLYGYRIDAE 



POLYGYRA STENOTREMA (Ferussac) 



Shells of the species Polygyra stenotrema and the species 

 Polygyra hirsuta may be distinguished from all others in Illinois 

 by a little notch on the base of the peristome and by a long, 



curved plait located on the parie- 



^^.^Z^^^^^^^^ tal wall. This fold in stenotrema 



is so large that it almost closes 

 the aperture. The brownish shell 

 of stenotrema is less than one-half 

 inch (10 mm.) in diameter and 

 much wider than high. It has 5 

 whorls. The upper end of the 

 heavy, curved parietal plait fits into a baylike cavity in the outer 

 lip or peristome. The lower part of the peristome is thickened 

 and has a small notch near the middle. The surface of the shell 

 is covered with small hairlike projections from the epidermis. 

 The large white lamella which completely hides the aperture 

 when the shell is viewed from the front is its chief distinguishing 

 character. 



This is typically a southern species, which is abundantly 

 distributed throughout Tennessee, Alabama and Georgia. The 

 only lot from Illinois which has been examined by the author 

 was collected by a survey party in an old quarry near Elizabeth- 

 town, Hardin County, on the Ohio River. 



Polygyra stenotrema is abundant in the southern part of 

 Indiana and is distributed up the Wabash Valley as far as 

 Parke County. The Illinois specimens of Hardin County are 

 evidently emigrants from Indiana. The species should be found 

 in other places in Illinois along the Ohio and Wabash rivers, 

 but diligent search during several seasons has failed to discover 

 it in the localities examined. 



In the Classified Catalogue of American Land Shells by 

 Pilsbry and Johnson, published in 1897, stenotrema is listed as 

 from Henry County, Illinois. This record is republished in 

 A Catalogue of the Mollusca of Illinois. Xo specimens of steno- 

 trema have recently been collected from Henry County, and 

 none occurs in the Nason or Hinkley collections in the Natural 

 History Museum of the University of Illinois. Because Henry 

 County is rather far north for stenotrema. the record for this 

 county should be viewed with suspicion. 



