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| 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 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.
Representation in Britain and Ireland. Pyramidula (1, “Rock snail”).
Illustrations. • Pyramidula rupestris (Taylor). PYRAMIDULIDAE. Pyramidula rupestris (Draparnaud), "Rock Snail", mature shells 2.5–3.0 mm. From Taylor (1914). • Pyramidula rupestris, with Discidae, Euconulidae, Punctidae, 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’.
