''Athearnia crassa'', the boulder snail, was a species of

freshwater snail Freshwater snails are gastropod mollusks which live in fresh water. There are many different families. They are found throughout the world in various habitats, ranging from ephemeral pools to the largest lakes, and from small seeps and springs ...

in the family

Pleuroceridae Pleuroceridae, common name pleurocerids, is a family of small to medium-sized freshwater snails, aquatic gilled gastropod mollusks in the superfamily Cerithioidea.These snails have an operculum and typically a robust high-spired shell. Reprodu ...

. It was native to the United States, where it was known from Alabama, Georgia, Tennessee, and Virginia. It is now

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

References

Molluscs of the United States Pleuroceridae Extinct gastropods Gastropods described in 1841 Taxa named by Samuel Stehman Haldeman Taxonomy articles created by Polbot {{Pleuroceridae-stub