POLYGYRIDAE 49 



POLYGYRA ALBOLABRIS (Say)* 



The common white-lipped snail is one of the largest found 

 in Illinois, and shell specimens measuring P/4 inches (27-33 

 mm.) in diameter are not uncommon. It is imperforate, of a 

 uniform yellowish-horn color and 

 has a spire that is dome shaped. 

 The aperture is usually without 

 denticulations, and the wide and 

 rather heavy peristome forms a 

 flattened expansion bordering the 

 aperture. The shell of this species 

 has 5^ whorls. 



The animal is variable in color, shading from cream on the 

 body to gray, black or brown on the head. 



This fine species of land snail is found in all parts of Illinois, 

 although the localities are rather widely separated. In habitat 

 the species seems to prefer forests of oak, hickory, elm and 

 walnut where there is a forest debris of long accumulation. 



Polygyra albolabris albolabris (Say). In the shell of the 

 typical variety, shown in the figure, the spire is high and the 

 peristome is wide and flattened. The surface is dull. This 

 variety is found mostly in the northern part of the state, north 

 of Vermilion County. The white-lipped snail is subject to con- 

 siderable variation from the typical, some of which appears to 

 be coincident with geographic distribution. The variations are 

 noted below. 



Polygyra albolabris alleni (Wetherby). The spire of this 

 variety is more depressed than that of the typical form, and 

 the peristome is narrower and inclined to be rounded. The 

 surface is shining, almost polished in some specimens. The lower 

 part of the peristome has a prominent denticle or callus which 

 is not so conspicuously developed in the typical form. This 

 variety is confined to the southern part of Illinois and has not 

 been seen north of Clark County. 



Polygyra albolabris dentata (Tryon). This unimportant 

 variety has a shell about an inch (27 mm.) in diameter. It is 

 distinguished by having a small denticle on the parietal wall. 

 The variety dentata is very rare in Illinois and has been recorded 

 only from Cook County in the northern part of the state and 

 from Williamson County in the southern part. 



