Cerithiopsidae are a family of very small and minute sea snails, marine gastropod molluscs or micromollusks in the informal group Ptenoglossa.
Marstonia ogmorhaphe, common names the royal marstonia or royal springsnail, is a minute species of freshwater snail, an aquatic gastropod mollusk or micromollusk in the family Hydrobiidae, the mud snails.