Hydrobiidae

Hydrobiids
Paludestrinidae
Pyrgulidae
Snails, Spring
Spring snails

World register of marine species, via WWW, Dec. 13, 2017 (Hydrobiidae. Rank: Family. Superfamily Truncatelloidea, Order Littorinimorpha. Synonymised names: Nymphophilinae, Paludestrinidae, Pyrgulidae; Lithoglyphidae listed separately as an accepted family within Truncatelloidea. Common name: Spring snails) Hydrobia (Common name: mud snails)
NCBI taxonomy browser, Dec. 18, 2017 (Hydrobiidae. Rank: family. Synonym: Pyrgulidae. Superfamily Truncatelloidea, Infraorder Littorinimorpha, (no rank) Hypsogastropoda, Subclass Caenogastropoda, Class Gastropoda; Lithoglyphidae separately listed another family within Truncatelloidea)
Worldwide mollusc species data base, via WWW, Dec. 18, 2017 (Family Hydrobiidae. Truncatelloidea [Superfamily] - Littorinimorpha [Order] - Caenogastropoda [Subclass]; family Lithoglyphidae has separate entry)
Wikipedia, Dec. 18, 2017 (Hydrobiidae, commonly known as mud snails, is a large cosmopolitan family of very small freshwater and brackish water snails with an operculum; they are in the order Littorinimorpha)
Wiktionary, Dec. 18, 2017 (hydrobiid (plural hydrobiids): (zoology) Any member of the Hydrobiidae)