VALLONIIDAE 117 



crawling the edge of the foot is somewhat wavy or crenulated. 

 The figure pictures Vallonia costata. 



The tiny Vallonia snails found in Illinois live in many 

 diverse habitats, from dry railroad embankments to wet flood- 

 plain areas. They are found in civilization more often than any 

 other Illinois snail and are observed in cellars, in yards of 

 residences and other similar places. Frequently they are found 

 under wet boards in shady places. They are more gregarious 

 than any other Illinois snail, and sometimes hundreds of speci- 

 mens are found in one place. 



The genus J^allonia divides into two distinct groups. In one 

 group are the species having a shell that is almost smooth 

 and a sculpture consisting of fine lines of growth. In the second 

 group are the species having a shell marked by many erect, 

 more or less equally spaced membranous ribs. Of the species 

 found in Illinois, Vallonia pulchella and Vallonia excentrica 

 belong to the smooth group, and Vallonia costata and Vallonia 

 parvula belong to the costate or ribbed group. 



The family Valloniidae is an old one and its species are 

 distributed wxll over the world, including North America, 

 Asia, Europe and northern Africa. It has been introduced into 

 Australia and the Island of Mauritius. Because of their small 

 size, specimens of Valloniidae are often inadvertently trans- 

 ported on greenhouse plants. 



Key to Species 



1. Shell costate, provided with projecting membranous ribs, 



pp. 116, 119 2 



Shell almost smooth, showing onlv fine growth lines, p. 

 118 ■ 3 



2. Umbilicus comparatively small; spire slightly elevated. . . . 



costata^ p. 1 19 



Umbilicus wide; spire not elevated parvula^ p. 119 



3. Shell straw colored; umbilicus ovate because of a rapid ex- 



pansion near latter halt of body whorl excentricay p. 118 



Shell clear-glass colored; umbilicus round pulchella^ p. 118 



(NO 



The beetle loves his unpretending track, 



The snail the house he carries on his back; 



The far-fetched worm with pleasure would disown 



The bed we give him though ot softest down; 



A noble instinct; in all kinds the same, 



All ranks! 



— William Wordsworth, Liberty 



