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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.
Eyes at the bases of the tentacles.
The shell operculate (this thick, somewhat calcified, concentrically lined); rising-spiral; 5 whorled, or 6 whorled; typically dextral; 5–13(–16) mm in its maximum dimension; higher than wide; 5–13(–16) mm high; about 3.25–8.5(–10.4) mm wide; height about 1.5–1.55 x the width; with the body whorl predominating and the spire small and short. The height of the spire about 0.3–0.35 x that of the shell. The spire acute to obtuse. The shell inverted-pyriform; deeply sutured (very deeply so in B. leachii). The whorls neither shouldered nor keeled. The aperture round to oval; with neither teeth nor calluses. The shell with an umbilicus to without an umbilicus. The umbilicus small (small). The shell thick-lipped; thin and translucent to opaque; horn-coloured; plain (glossy).
General biology, ecology. Freshwater aquatic. Breathing via a single gill attached within the mantle cavity. In large bodies of well oxygenated, slow moving or still, hard water.
The individuals either male or female (not hermaphrodite).
Classification. Gastropoda; Prosobranchia.
Representation in Britain and Ireland. Bithynia (2, “Bithynia snails”).
Illustrations. • Bithynia leachii and Bithynia tentacula (Reeve). BITHYNIIDAE. 1, Bithynia tentacula L., "Common Bithynia". 2, Bithynia leachii (Sheppard), "Leach's Bithynia". From Reeve (1863), with approximate scales added. • Bithynia leachii and Bithynia tentaculata, 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’.
