What is "polygyridae"

Polygyridae is a family of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the superfamily Helicoidea.

The Polygyridae make up a significant proportion of the land snail fauna of eastern North America, and are also found in western North America, northern Central America, and are present on some Caribbean islands. The definitive reference to the group is Henry Pilsbry's 1940 monograph.