| | The families of non-marine molluscs of Britain and Ireland (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.
Hermaphrodite.
Classification. Gastropoda; Pulmonata.
Representation in Britain and Ireland. Paralaoma (1), Punctum (1, “Dwarf snail”).
Illustrations. • Punctum pygmaeum (Taylor). PUNCTIDAE. 2, Punctum pygmaeum (Draparnaud), "Dwarf Snail", mature shells 1.2–1.5 mm. From Taylor, 1914. • Punctum pygmaeum, with Discidae, Euconulidae, Pyramidulidae, Valloniidae, Vitrinidae (Adams). PYRAMIDULIDAE. 1, Pyramidula rupestris (Draparnaud), "Rock Snail". PUNCTIDAE. 2, Punctum pygmaeum (Draparnaud), "Dwarf Snail". VALLONIIDAE. 3, Vallonia pulchella (Müller), "Smooth Grass Snail, Beautiful Grass Snail"; 4, Acanthinula aculeata (Müller), "Prickly Snail"; 5, Spermodea lamellata (Jeffreys), "Plated Snail"). DISCIDAE. 6, Discus rotundatus (Müller), "Rounded Snail, or Radiated Snail"). VITRINIDAE. 7, Vitrina pellucida (Müller), "Pellucid Glass Snail". EUCONULIDAE. 8, Euconulus fulvus agg., probably E. fulvus (Müller), "Tawny Glass Snail". From Adams (1896).
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, 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. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2005 onwards. The families of non-marine molluscs of Britain and Ireland (slugs, snails and mussels). Version: 5th August 2019. delta-intkey.com’.
