The families of British non-marine molluscs (slugs, snails and mussels)
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 of 19 separate plates.
The shell inoperculate; rising-spiral; 3.5–4 whorled; typically dextral; 1.2–2 mm in its maximum dimension; wider than high; about 0.7–0.85 mm high (Punctum pygmaeum), or 1.2–1.3 mm high (Paralaoma caputspinulae); 1.2–1.5 mm wide (P. pygmaeum), or 1.8–2 mm wide (Paralaoma caputspinulae); height about 0.62–0.7 x the width; with the body whorl predominating and the spire small and short. The height of the spire about 0.15–0.21 x that of the shell. The spire obtuse. The shell cochleate; deeply sutured. The body whorl moderately convex. The whorls of the spire moderately convex. The whorls neither shouldered nor keeled; not conspicuously transversely ridged (but with numerous very fine, regular growth ridges, lending a sheen). The aperture with neither teeth nor calluses. The shell with an umbilicus. The umbilicus large and wide (shallow). The shell thin-lipped (the mouth edge thin and brittle, not deflected); opaque; golden brown in Punctum; plain.
General biology, ecology. Terrestrial. In leaf litter, etc., in moist places.
Classification. Gastropoda; Pulmonata.
British representation. Paralaoma (1), Punctum (1, Dwarf snail).
Illustrations. • Punctum pygmaeum (Taylor). • Punctum pygmaeum, with Discidae, Euconulidae, Pyramidulidae, 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. http://delta-intkey.com’.