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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 shell operculate (this horny and thin or fairly thick, concentrically lined); rising-spiral; 6–7 whorled; typically dextral; 25–35 mm in its maximum dimension (V. viviparus), or 30–40 mm in its maximum dimension (V. contectus); higher than wide; 25–35 mm high (V. viviparus), or 30–40 mm high (V. contectus); about 18–26 mm wide (V. viviparus), or 23.5–31.8 mm wide (V. contectus); height about 1.2–1.3 x the width. The height of the spire about 0.22–0.25 x that of the shell. The shell inverted-pyriform; deeply sutured (between all the whorls). The whorls neither shouldered nor keeled. The aperture almost round; with neither teeth nor calluses. The shell with an umbilicus, or without an umbilicus. The umbilicus small (deep and distinct, in V. contectus only). The shell thick-lipped; opaque; dark greenish with darker bands; conspicuously colour-patterned.
General biology, ecology. Freshwater aquatic. Breathing via a single gill attached within the mantle cavity. In large bodies of well oxygenated, still or slow-moving water. Suspension feeders, lying for long periods in mud with the mouth uppermost.
The individuals either male or female (not hermaphrodite); viviparous.
Classification. Gastropoda; Prosobranchia.
Representation in Britain and Ireland. Viviparus (2, “River snails”).
Illustrations. • Viviparus contectus and Viviparus viviparus (Reeve). VIVIPARIDAE. 1, Viviparus contectus (Millet), "Lister's River Snail". 2, Viviparus viviparus (L.), "Common River Snail". From Reeve (1863), with approximate dimensions added. • Viviparus contectus and Viviparus viviparus, with other Gastropoda-Prosobranchia (Adams). NERITIDAE. 4, Theodoxus fluviatilis (Linn.), "River Nerite". VIVIPARIDAE. 5, Viviparus contectus (Millet), "Lister's River Snail"; 6, Viviparus viviparus (Linn.), "Common River Snail". BITHYNIIDAE. 7, Bithynia tentaculata (Linn.), "Common Bithynia"; 8, Bithynia leachii (Sheppard), "Leach's Bithynia". VALVATIDAE. 9, Valvata piscinalis (Müller), "Common Valve Snail"; 10, Valvata cristata Müller, "Flat Valve Snail". HYDROBIIDAE. 11, Mercuria confusa (Frauenfeld), "Swollen Spire Snail". 12, Hydrobia ventrosa (Montagu), "Spire Snail". 13, Potamopyrgus antipodarum (Gray), "Jenkins's Spire Snail". POMATIASIDAE. 14, Pomatias elegans (Müller), "Round-mouthed Snail". ACICULIDAE. 15, Acicula fusca (Montagu), "Point Snail", with detail of the operculum. 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’.
