|
| 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 one pair of tentacles only. Eyes at the bases of the tentacles.
The shell operculate (this thick, testaceous, somewhat calcified); rising-spiral; 4.5–5 whorled; typically dextral; 12–16 mm in its maximum dimension; higher than wide; 12–16 mm high; 9–11.5 mm wide; height about 1.4 x the width; with the body whorl predominating and the spire small and short to high-spired and tapered gradually from the body whorl. The height of the spire about 0.3 x that of the shell. The shell inverted-pyriform; deeply sutured (between all the whorls). The body whorl only slightly convex. The whorls of the spire feebly convex. The whorls neither shouldered nor keeled. The aperture round; with neither teeth nor calluses. The shell with an umbilicus. The umbilicus small (small, but deep). The shell thick-lipped; opaque (thick and solid, with a reticulate sculpture of fine spiral and transverse ribs, the former more pronounced at least near the base of the shell); light pinkish or greyish violet to yellowish, with darker streaks or spots; fairly conspicuously colour-patterned to plain.
General biology, ecology. Terrestrial. Breathing air directly via the lung-like mantle cavity. Strictly calcicole, burrowing into in loose rubble in hedge banks, quarries, open woods, cliffs, and maritime grassland.
The individuals either male or female (not hermaphrodite) (the shells of females often slightly larger).
Classification. Gastropoda; Prosobranchia.
Representation in Britain and Ireland. Pomatias (1, “Round-mouthed snail”).
Illustrations. • Pomatias elegans, with Acicula fusca (Reeve). POMATIASIDAE. 1, Pomatias elegans (Müller), "Round-mouthed Snail". ACICULIDAE. 2, Acicula fusca (Montagu), "Point Snail". From Reeve (1863), with approximate scales added. • Pomatias elegans, 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 crista 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’.
