LAND SNAILS 



Native to Illinois 



Class GASTROPODA 



The class Gastropoda includes all snails, those which live in 

 the ocean, in lakes, rivers and pools, as well as those which live on 

 land. 



Order PROSOBRANCHIATA 



In the order Prosobranchiata are the snails which breathe by 

 means of plumelike gills. The great majority of the species of this 

 order live in the ocean, but many live in fresh water, and not a few 

 live on land far removed from water. Only one species, however, is 

 known from Illinois. 



Order PULMONATA 



The order Pulmonata includes all but one of the species of land 

 snails which live in Illinois. The animal breathes by means of a 

 lung, as is explained in the introductory chapter of this fieldbook. 



Suborder STYLOMMATOPHORA 



Most families, genera and species of snails living in Illinois are 

 included in the suborder Stylommatophora of the order Pulmonata. 

 This suborder embraces most of the land snails of the world. 



Animals of this suborder have four tentacles, arranged as 

 pairs. The superior, or longer, tentacles with the snail's eyes at 

 the tips are retractile. The inferior tentacles are very short. 



Suborder BASOMMATOPHORA 



Animals of this suborder of Pulmonata have tentacles that are 

 more or less flattened and triangular or subcylindrical. The tentacles 

 are contractile but not invertible as in the true land snails, the sub- 

 order Stylommatophora. The eyes are placed at the inner base of 

 the tentacles and not at the end, as are those of the true land snails. 

 Most species of this group live in or near fresh water, though they 

 breathe by a lung, much as do the Stylommatophora. 



In the following pages , the actual width or length of the specimen 

 is represented by a line near the figure. 



[37] 



