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 animal with two pairs of tentacles. Eyes at the tips of the posterior tentacles. The jaw arcuate, with a vertical central keel ending in a median projection on the lower edge (cf. Limacidae, etc.).

The shell inoperculate; rising-spiral (but often only slightly raised); 3.5–6(–7) whorled; typically dextral; wider than high; 2.2–15 mm wide; height about 0.43–0.59 x the width; with the body whorl predominating and the spire small and short. The height of the spire about 0.1–0.18 x that of the shell, or 0.2–0.28 x that of the shell (Zonitoides). The spire obtuse. The shell more or less discoid, or cochleate; deeply sutured. The body whorl moderately convex to very strongly convex. The whorls of the spire feebly convex to moderately convex. The whorls neither shouldered nor keeled. The aperture with neither teeth nor calluses. The shell with an umbilicus to without an umbilicus. The umbilicus small to large and wide (variable in depth, with, and symmetry). The shell thin-lipped (the mouth edge delicate, not deflected); in life, mostly thin and translucent (and usually glossy, but often becoming opaque after death of the animal); often clear horn-coloured, fawn, brownish or whitish; plain. Morphological comments. The body of the animal is often tinted bluish.

General biology, ecology. Terrestrial. In vegetation and ground litter, under logs and stones, etc., in diverse habitats.

Hermaphrodite. Courtship involving exchanges of ‘love darts’ prior to mating (the Zonitoides species), or not involving ‘love darts’; the darts calcareous.

Classification. Gastropoda; Pulmonata.

British representation. “Glass snails” and “Garlic snails”: Aegopinella (2), Nesovitrea (2), Oxychilus (4), Vitrea (3), Zonitoides (2).

Illustrations. • Aegopinella nitidula, Oxychilus alliarius, O. cellarius, O. draparnaudii, O. helveticus (Taylor). • Aegopinella pura, Nesovitrea hammonis, Vitrea contracta, V. crystallina, Zonitoides excavatus, Z. nitidus (Taylor). • Live animals: Aegopinella, Nesovitrea, Oxychilus, Vitrea, Zonitoides (Taylor). • Aegopinella, Nesovitrea, Oxychilus, Vitrea, Zonitoides (Adams). • Love darts of Zonitoides, with some from Helicidae (Taylor). • Aegopinella, Neesovitrea, Oxychilus, Vitrea, Zonitoides (Reeve).

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.’.