North American Land Snails

NORTH AMERICAN LAND SNAILS. North American genera of the Helices may be grouped by peculiarities of the lip of the shell into four classes. Certain notable exotic genera will be mentioned with natives in their proper class under this simple key, made by Dr. Pilsbry for beginners.

A. Shell with thin, sharp lip, not expanded: Genus Pyramidula Genus Glyptostoma B. Shell with blunt, thick lip, not expanded:

Genus Polygyrella C. Shell with lip expanded, not flatly reflexed: Genus Epiphragmophora Genus Vallonia D. Shell with lip decidedly reflexed, often toothed: Genus Polygyra.