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 (the operculum horny, with spiral growth lines); rising-spiral; 4–8 whorled (?); typically dextral; 1.7–2 mm in its maximum dimension (Paludinella), or 4–6 mm in its maximum dimension (Assiminea); higher than wide; 1.7–2 mm high (Paludinella), or 4–6 mm high (Assiminea); about 1.5–1.8 mm wide (Paludinella), or 2.6–3.9 mm wide (Assiminea); height about 1.2 x the width (Paludinella), or 1.6 x the width (Assiminea); with the body whorl predominating and the spire small and short (Paludinella), or high-spired and tapered gradually from the body whorl (Assiminea). The height of the spire about 0.23 x that of the shell (Paludinella), or 0.38 x that of the shell (Assiminea). The spire acute (in A. grayana), or obtuse (in Paludinella). The shell shortly turretiform (i.e., conical, in A. grayana), or inverted-pyriform (in Paludinella); shallowly sutured (in A. grayana), or deeply sutured (in Paludinella). The whorls neither shouldered nor keeled. The aperture with neither teeth nor calluses. The shell without an umbilicus. The shell thick-lipped; opaque; plain.

General biology, ecology. Terrestrial, or semi-marine. Breathing air directly via the lung-like mantle cavity. Coastal, found in shingle and plant dèbris around the high tide mark, sometimes submerged in brackish water, but more terrestrial than aquatic.

The individuals either male or female (not hermaphrodite).

Classification. Gastropoda; Prosobranchia.

British representation. Assiminea (1, “Dun Sentinel”), Paludinella (1).

Illustrations. • Assiminea grayana, living animal (Reeve). • Assiminea grayana shell (Ellis).

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.’.