^OLYGYRIDAE 59 



POLYGYRA HIRSUTA (Say) 



One of the smallest of this genus of snails, Polygyra hirsuta 

 tias a shell measuring but slightly more than one-fourth inch 

 (7-9 mm.) in diameter. It differs from its relative, Polygyra 

 stenotrema, in its smaller size, in 

 its much smaller parietal plait, 

 ivhich does not seem to close the 

 aperture when observed from the 

 front view, and in the notch on 

 the lower lip, which is larger and 

 is not centrally placed as it is in 

 sfenotrema. The brown shell of 

 hirsuta, also, is more nearly globular in shape and is much more 

 hairy. The hirsute processes of the epidermis are placed in 

 regular rows and stand out from the shell to a considerable 

 distance. This regularity is seen only in fresh, unworn speci- 

 mens, as the hairs are easily rubbed off. The umbilical region 

 is more deeply indented in hirsuta than in stenotrema. The 

 differences between these two closely related species are well 

 shown by the figures in this volume. 



The animal oi hirsuta is whitish, with the head, eye peduncles 

 and tentacles slate colored. The foot is semitransparent and is 

 very narrow when extended. 



This is one of the commonest and most widely distributed 

 snails in Illinois. Its usual habitat is in forests along river 

 valleys where there is a growth of oak, hickory, elm, basswood 

 and box elder trees. The snail is found under and in old logs, 

 under forest debris and sometimes in the washed up brush and 

 other material deposited by high water. It seems to prefer moist 

 locations, but has been found in some places which are relatively 

 dry. 



The distribution of hirsuta includes both the United States 

 and Canada. It may be found in Canada and Minnesota, south 

 to Kansas and eastward to New York and Alabama. 



Polygyra hirsuta was among the first species of land snails 

 described by Thomas Say. Since the original description, pub- 

 lished in 1817, is accurate and very minute, later authors have 

 not improved upon it. Say had a peculiar insight into the details 

 which separate one species from another, and his descriptions 

 are models of accuracy in this respect. 



