| | 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 set on small protuberances at the bases of the tentacles.
The shell operculate (the operculum excentric, thin and horny); rising-spiral; 5–5.5 whorled; typically dextral; 2.2–2.5 mm in its maximum dimension; higher than wide; 2.2–2.5 mm high; 0.8 mm wide; height about 2.5 x the width; high-spired and tapered gradually from the body whorl. The height of the spire about 0.6 x that of the shell. The spire obtuse. The shell almost cylindrical (gently tapered from the body whorl); shallowly sutured (the suture appearing double, with the inner surface of the shell showing through where is is attached to the preceding whorl). The body whorl only slightly convex to moderately convex. The whorls of the spire feebly convex. The whorls neither shouldered nor keeled (almost straight-sided in section). The shell conspicuously and regularly striated across the whorls (with widely spaced, sharply incised transverse grooves). The aperture pear-shaped; with neither teeth nor calluses. The shell with an umbilicus. The umbilicus very small (minute). The shell thin-lipped (save where the columellar edge of the mouth deflects over the umbilicus); thin and translucent (somewhat transparent); light brown; plain (very glossy, striated across the whorls).
General biology, ecology. Terrestrial. Breathing air directly via the lung-like mantle cavity. In moist moss and leaf litter, mainly in old deciduous woodland; tolerating non-calcareous soils.
The individuals either male or female (not hermaphrodite).
Classification. Gastropoda; Prosobranchia.
Representation in Britain and Ireland. Acicula (1, “Point snail”).
Illustrations. • Acidula fusca, 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). • Acicula fusca, with Pomatias elegans (Reeve). POMATIASIDAE. 1, Pomatias elegans (Müller), "Round-mouthed Snail". ACICULIDAE. 2, Acicula fusca (Montagu), "Point Snail". From Reeve (1863), with approximate scales added.
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’.
