Gastropods are the most successful class of mollusks, if you go by number of species. Gastropod shells consist of one piece that grows in a coiled pattern, the organism moving into larger chambers in the shell as it becomes larger. Land snails are also gastropods. These tiny freshwater snail shells occur in the recent Shavers Well Formation in southern California. The coin is 19 millimeters across. Learn more details about gastropods
from About Animals Guide Laura Klappenbach.