ZONITIDAE 81 



Genus VENTRIDENS W. G. Binney & Bland 



Members of the genus Ventridens are like large specimens 

 of Euconulus. Shells of Fentridens have a dome-shaped spire, 

 a body whorl with a rounded base and a very small umbilical 

 perforation. They have 6 or 7 closely coiled whorls which are 

 sculptured with fine growth lines arranged in the form of 

 flattened ribs. These lines disappear on the base of the shell. 



Two species of Fentridens have been found in Illinois. In 

 the older books on the Mollusca these species are arranged 

 under Zonites and Gastrodonta. 



Key to Species 



Aperture a half circle; spire elevated; color yellowish. . . . ligerus, p. 81 



Aperture crescent shaped; spire depressed; color whitish 



demissus, p. 82 



VENTRIDENS LIGERUS (Say) 



The yellowish horn-colored shell of the snail Fentridens 

 ligerus is a little over one-half inch (13-15 mm.) in diameter. 

 Its height equals three-fourths to five-sixths the diameter. On 

 the base of the shell, near the aper- 

 ture, ligerus has a bright yellow 

 callus. 



The animal is of uniform dark 

 slate color on the upper surface, 

 somewhat paler on the posterior 

 part and on the sides of the foot. 

 It has long, pointed eye peduncles. 



Fentridens ligerus is found over 

 much of Illinois, but is more abundant in the southern than in 

 the northern half. It is particularly abundant in the hill and 

 bluff region of the extreme southern part of the state. It lives 

 in a variety of habitats and appears equally at home in the 

 ravines of small streams, on the bluffs of large river valleys, and 

 in floodplain and lowland areas bordering streams. In the blufiE 

 region, the forest habitat contains oak, elm, locust, dogwood 

 and some sumac. In the floodplain areas, the habitat contains 

 maple, elm, cottonwood, willow and oak. The species is found 

 under logs, in the brushwood of floodplains and in limestone 

 rock debris. 



