ZONITIDAE 



79 



ish horn-colored shell of arborciis measures less than one- 

 fourth inch (5 mm.) in diameter. The spire is more depressed, 

 the umbilicus is smaller and the base of the shell flatter than in 

 nitidus. These three points will usually separate the two species. 



The animal of arboreus is black or bluish on the head and 

 upper parts of the body. The posterior 

 part is whitish and somewhat trans- 

 parent. The foot is narrow. 



Among the most abundant of the 

 land snails found in Illinois, arboreus is 

 distributed throughout the entire state. 

 There is scarcely a county from which 

 this species has not been reported. Its 

 habitat is varied. It is found in deep 

 woods, in isolated woodlands, on bluffs 

 and the banks of streams, among shrub- 

 bery and even in the hot environment 

 of railway embankments. It lives under 

 loose bark, under fallen timber of all 

 sorts, in grass and under rock piles. It 



is our commonest snail, invading the farm woodlot, the village 

 or city yard and the small fruit and truck garden. In several 

 places outside Illinois, arboreus has become an enemy to agri- 

 culture by feeding on tender vegetation, or by damaging the 

 root ends as it does in Louisiana sugar cane plantations. 



ZONITOIDES NITIDUS (Muller) 



The shell of Zonitoides nitidus is about one-fourth inch 

 (6.0-7.5 mm.) in diameter. The spire is only slightly elevated, 

 the 5 whorls rising to about half the height of the diameter. 

 The shining and somewhat polished surface of the shell is yel- 

 lowish in color. Conspicuous surface sculpture, such as is found 

 in the shell of limatulus, is absent in that of nitidus, which is 

 marked only with fine lines of growth. The rounded base of the 

 nitidus shell has a large, deep umbilicus in the center. 



The animal resembles that of Zonitoides arboreus. 



In Illinois Zonitoides nitidus lives in decaying logs and under 

 forest debris on floodplains of streams. It shows a preference 

 for muddy places. Trees usually characteristic of its habitat 

 are elm. oak, maple or hickory. The species is known at present 



