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 shell inoperculate; rising-spiral; 4.5 whorled; typically dextral; wider than high; 1.5–2 mm high; 2.5–3 mm wide; height about 0.56 x the width; high-spired and tapered gradually from the body whorl. The height of the spire about 0.39 x that of the shell. The spire obtuse. The shell cochleate; deeply sutured. The body whorl very strongly convex. The whorls of the spire moderately convex to very strongly convex. The whorls bluntly shouldered. The aperture gibbous; with neither teeth nor calluses. The shell with an umbilicus. The umbilicus large and wide (and deep). The shell thin-lipped (the edge brittle); opaque (the well defined growth ridges bestowing a silky aspect); dark horn-coloured or reddish brown, weathering to almost white; plain.

General biology, ecology. Terrestrial. Grazing nocturnally or in wet weather on lichens and algae on limestone rocks and walls, or associated with calcareous mortar, in locations exposed to the sun.

Hermaphrodite; viviparous.

Classification. Gastropoda; Pulmonata.

British representation. Pyramidula (1, “Rock snail”).

Illustrations. • Pyramidula rupestris (Taylor). • Pyramidula rupestris, with Discidae, Euconulidae, Punctidae, Valloniidae, Vitrinidae (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.’.