The families of British non-marine molluscs (slugs, snails and mussels)


L. Watson and M. J. Dallwitz


Morphology. Snails, with a conspicuous, spiral, univalve shell.

The shell operculate (this thin, horny, spirally lined); rising-spiral; 4 whorled, or 5–6 whorled, or 7–8 whorled; typically dextral; 2.5–6(–9) mm in its maximum dimension; higher than wide; 2.5–6(–9) mm high; height about 1.7–2.3 x the width; high-spired and tapered gradually from the body whorl. The height of the spire about 0.4–0.5 x that of the shell. The spire acute to obtuse. The shell inverted-pyriform, or tear-shaped, or turretiform; deeply sutured (between all the whorls). The whorls neither shouldered nor keeled. The aperture oval; with neither teeth nor calluses. The shell with an umbilicus. The umbilicus small (small). The shell thick-lipped; thin and translucent to opaque; horn-coloured; plain.

General biology, ecology. Freshwater aquatic, or semi-marine. Breathing via a single gill attached within the mantle cavity. Variously in still, slow or fast moving, fresh or brackish water.

The individuals either male or female (not hermaphrodite).

Classification. Gastropoda; Prosobranchia.

British representation. Hydrobia (3, “Spire snails”), Heleobia (1), Mercuria (1, “Swollen Spire snail”), Marstoniopsis (1, “Taylor’s Spire snail”), Potamopyrgus (1, “Jenkins's Spire snail”).

Illustrations. • Hydrobia ventrosa, H. ulvae, Mercuria confusa, Potamopyrgus antipodarum (Ellis). • Hydrobia ventrosa, Mercuria confusa, Potamopyrgus antipodarum (with other Gastropoda-Prosobranchia: Adams).

To view the illustrations with detailed captions, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2005 onwards. The families of British non-marine molluscs (slugs, snails and mussels). Version: 4th January 2012.’.