« Shell minute to small, usually 1-10mm in height (but up to 50mm), dextrally coiled, planispiral to aciculate, phaneromphalous to cryptomphalous, with about 2-8 whorls. Body whorl often loosened, shell sometimes partially uncoiling to assume a corkscrew or horn-like shape. Shell thin to fairly solid, transparent to white. Periostracum generally thin, rarely elaborated as hair-like or other projections; often colored, usually uniformly but rarely with band-like patterns. Aperture holostomatous, sometimes thickened, sinuous, deflected or flared, but without notches, canals, siphonal grooves, or denticulations. Shell usually smooth except for collabral growth-lines, but occasionally with sculpture of reticulations, carinae, spines, or cords. Protoconch usually paucipsiral, rarely multispiral, usually dome-like, smooth or with sculpture of wrinkles, pits, or spiral lines. » – Kabat & Hershler: “The Prosobranch Snail Family Hydrobiidae (Gastropoda: Rissooidea): Review of Classification and Supraspecific Taxa”, Smithsonian Contributions to Zoology vol.547, Washington 1993, p.5.   Nota bene that a generic description is almost impossible without using molecular analysis: studies only based upon shell morphology provide only unusable sentences, because the shells, in this familly, bear nearly identical shapes, and their variations inside a genus overlap with those inside other genera.
 

Whorls far less convex than in the other genera. Periostracum slightly thicker.