The families of British non-marine molluscs (slugs, snails and mussels)
Morphology. Snails, with a conspicuous, spiral, univalve shell.
The animal with two pairs of tentacles. Eyes at the tips of the posterior tentacles.
The shell mostly with a clausilium, which functions as an operculum when the animal retracts (a flexible, spoon-shaped plate, attached to the columella, which blocks the entrance when the animal withdraws), or inoperculate (and lacking a clausilium, in Balea); rising-spiral; 9–13 whorled; typically sinistral; higher than wide; 8–17 mm high; 2.2–4 mm wide; height about 3.7–4.3 x the width; high-spired and tapered gradually from the body whorl. The height of the spire about 0.64–0.7 x that of the shell. The shell fusiform, or tear-shaped; shallowly sutured to deeply sutured. The body whorl only slightly convex to moderately convex. The whorls of the spire feebly convex. The whorls neither shouldered nor keeled. The shell usually more or less conspicuously and regularly striated across the whorls (or finely ribbed), or not markedly striated across the whorls (e.g., glossy and somewhat translucent in Cochlodina laminata). The aperture relatively small, pear-shaped; bearing teeth (usually), or bearing calluses (sometimes in Balea). The columella folded. The shell somewhat thick-lipped; thin and translucent, or opaque; grey, yellowish- or reddish-brown, blackish or horn-coloured, but commonly bleached grey; conspicuously colour-patterned, or conspicuously colour-patterned to plain (sometimes streaked with white).
General biology, ecology. Terrestrial. Often in moss or ground litter, or lichen-encrusted walls.
Hermaphrodite; viviparous (Balea), or oviparous.
Classification. Gastropoda; Pulmonata.
British representation. Door snails, Tree snails: Balea (2), Clausilia (2), Cochlodina (1), Macrogastra (1).
Illustrations. • Balea perversa, Clausilia spp. and Macrogastra rolphii, with Chondrinidaeidae, Cochlicopidae, Enidae, Ferussaciidae and Pupillidae (Ellis). • Balea biplicata, Balea perversa, Clausilia bidentata, Cochlodina laminata (live animal), Macrogastra rolphi (Reeve). • Balea, Clausilia, Cochlodina and Macrogastra, with Aciculidae, Cochlicopidae, Ellobiidae, Ferussaciidae (Adams).
To view the illustrations with detailed captions, go to the interactive key. This also offers 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.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2005 onwards. The families of British non-marine molluscs (slugs, snails and mussels). Version: 4th January 2012. http://delta-intkey.com’.