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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 thin, horny, spirally lined); rising-spiral; 4 whorled, or 5–6 whorled, or 7–8 whorled; typically dextral; 2.5–6(–9) mm in its maximum dimension; higher than wide; 2.5–6(–9) mm high; height about 1.7–2.3 x the width; high-spired and tapered gradually from the body whorl. The height of the spire about 0.4–0.5 x that of the shell. The spire acute to obtuse. The shell inverted-pyriform, or tear-shaped, or turretiform; deeply sutured (between all the whorls). The whorls neither shouldered nor keeled. The aperture oval; with neither teeth nor calluses. The shell with an umbilicus. The umbilicus small (small). The shell thick-lipped; thin and translucent to opaque; horn-coloured; plain.
General biology, ecology. Freshwater aquatic, or semi-marine. Breathing via a single gill attached within the mantle cavity. Variously in still, slow or fast moving, fresh or brackish water.
The individuals either male or female (not hermaphrodite).
Classification. Gastropoda; Prosobranchia.
Representation in Britain and Ireland. Hydrobia (3, “Spire snails”), Heleobia (1), Mercuria (1, “Swollen Spire snail”), Marstoniopsis (1, “Taylor’s Spire snail”), Potamopyrgus (1, “Jenkins's Spire snail”).
Illustrations. • Hydrobia ventrosa, H. ulvae, Mercuria confusa, Potamopyrgus antipodarum (Ellis). HYDROBIIDAE. 4, Hydrobia ulvae (Pennant), "Laver Spire Snail". 5, Mercuria confusa (Frauenfeld), "Swollen Spire Snail". 6, Hydrobia ventrosa (Montagu), Spire Snail". 7, Potamopyrgus antipodarum (Gray), "Jenkins's Spire Snail". From Ellis (1926). • Hydrobia ventrosa, Mercuria confusa, Potamopyrgus antipodarum (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’.
