| | 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 two pairs of tentacles. Eyes at the tips of the posterior tentacles.
The shell inoperculate; planispiral (Helicodonta), or rising-spiral (the rest, but some discoid, with the spire scarcely raised); (4–)5–7 whorled (mostly), or 8–10 whorled; typically dextral; (5–)6–40(–50) mm in its maximum dimension (wide), or 10–25(–40) mm in its maximum dimension (high); higher than wide (conspicuously so only in Cochlicella), or about as high as wide (more or less,in Trochoidea elegans, Helix aspersa, H. pomatia and Arianta arbustorum), or wider than high (mostly, at least somewhat); 3.5–50 mm high; 5–50 mm wide (the measurements and proportions reflecting great variation in sizes and shapes among, and sometimes within, the genera); height about 0.45 x the width (Helicodonta), or 0.59–1 x the width (mostly), or 1.8–2 x the width (Cochlicella); with the body whorl predominating and the spire small and short, or high-spired and tapered gradually from the body whorl. The height of the spire about 0.09–0.32 x that of the shell (mostly), or 0.57–0.66 x that of the shell (Cochlicella), or inapplicable to the planispiral in Helicodonta. The spire acute (in Cochlicella), or obtuse (mostly). The shell when not or scarcely higher than wide, discoid (in Helicella, and more or less so in Helicogona lapicida), or conical (in Trochoidea elegans and Cochlicalla barbara), or cochleate (most commonly), or subglobose to globose (in Helix aspersa and H. pomatia); when markedly higher than wide, i.e. in Cochlicella, tear-shaped, or turretiform; shallowly sutured, or deeply sutured, or shallowly sutured to deeply sutured. The whorls neither shouldered nor keeled (mostly), or shouldered (Perforatella subrufescens), or keeled (Trochoidea, Hygromia, Helicogona); conspicuously and regularly transversely ridged across the whorls, or not conspicuously transversely ridged. The aperture with neither teeth nor calluses. The shell with an umbilicus. The shell thick-lipped; opaque; variously white, yellow, pink, horn-coloured, or brown; conspicuously colour-patterned (often strikingly banded along or occasionally across the whorls), or plain.
General biology, ecology. Terrestrial. Mostly in dry, sunny, open, especially calcareous places, in quarries, stone walls, hedgerows, waste ground, gardens, etc.; but a few confined to moist and sheltered or marshy places, or woodland.
Hermaphrodite. The stalk of the bursa copulatrix with a diverticulum. Courtship involving exchanges of ‘love darts’ prior to mating; the darts calcareous (the darts exhibit characteristic shapes and sculpting, for example providing ready means of distinguishing C. hortensis from C. nemoralis - see illustrations).
Classification. Gastropoda; Pulmonata.
Representation in Britain and Ireland. Arianta (1, “Copse snail”), Ashfordia (1, “Silky snail”), Candidula (2, “Wrinkled snail”), Cepaea (2, “Grove snail and White-lipped snail”), Cernuella (1, “Striped snail, Zoned snail”), Cochlicella (2, “Pointed snails”), Helicodonta (1, “Cheese snail”), Helicella (1, “Heath snail”), Helicogona (1, “Lapidary snail”), Helix (including Cantareus) (2, “Garden snail”, and “Edible” or “Roman snail”), Hygromia (2, “Girdled snail and Hedge snail”), Monacha (2, “Carthusian snail and Kentish snail”), Perforatella (2, “Brown snail”), Ponentina (1), Trichia (3, including “Strawberry snail“ and “Hairy snail”), Theba (1, “White snail, Sandhill snail”), Trochoidea (2, “Top snails”).
Illustrations. • Arianta arbustorum: shell variation (Taylor). ARIANTA. 17, Arianta arbustorum (Linn.), "Copse Snail", mature shells 17–23 mm. From Taylor (1914). • Arianta arbustorum: shells (L.W.). HELICIDAE. Arianta arbustorum (L.), “Copse Snail”. Lathkil Dale, Derbyshire. May 1950. • Cepaea hortensis: shell variation (Taylor). CEPAEA. Cepaea hortensis (Müller), “White-lipped Snail”, mature shells 16–20 mm. From Taylor (1914). • Cepaea hortensis: diverse shells from one locality (L.W.). HELICIDAE. Cepaea hortensis (Müller), "White-lipped Snail". Miller's Dale, Buxton, Derbyshire. May 1949. • Cepaea nemoralis: shell variation (Taylor). CEPAEA. Cepaea nemoralis (Linn.): "Grove Snail", "Brown-lipped Snail", mature shells 18–25 mm. From Taylor (1914). • Cepaea nemoralis: shell variation from one locality (L.W.). Cepaea nemoralis (L.), "Brown-lipped snail". Upper and lower views of five shells, exemplifying variation in one population; collected from a roadside verge near Leek, Staffs. (red sandstone substrate) by L.W. in 1950. • Cernuella virgata: shell variation (Taylor). CERNUELLA. Cernuella virgata (da Costa), "Striped Snail, Zoned Snail", mature shells 9–18 mm. 1, Typical form, Lewes (T.S. Hillman). 2, var nigrescens Grat., Afton Downs, I. of Wight (C. Ashford). 3, var. rufulo-zonata Taylor, Langharne (G.W. Mellors). 4, var. albicans Grat., Newquay (J.H. James). 5, var. alba Taylor, Lewes (C.H. Morris). From Taylor (1895). • Cochlicella acuta: live animal (Reeve). HELICIDAE. Cochlicella acuta (Müller), "Pointed Snail". From Reeve (1863, with approximae scale added). • Helicella itala, shells (L.W.). HELICIDAE. Helicella itala (L.), “Heath Snail”. Mawgan Porth near Newquay, Cornwall. 18th Oct. 1943 (J. Armitage). • Helicogona lapicida: shell varieties (Taylor). HELICIGONA. Helicigona lapicida (Linn.), "Lapidary Snail", mature shells 15–20 mm. From Taylor (1914). • Helicigona lapicida (L.W.). Helicigona lapicida. Lathkill Dale, Derbyshire, under stones. May 1949. • Helix aspersa: shell varieties (Taylor). HELIX sensu stricto. Helix aspersa Müller, "Garden Snail" or "Common Snail", mature shells 30–40 mm. From Taylor (1914). • Helix aspersa: live animal (Reeve). Helix aspersa, from Reeve (1863). • Helix pomatia shells (Taylor). HELIX sensu stricto. Helix pomatia Linn., "Roman Snail", "Edible Snail", "Vine Snail" or "Apple Snail", mature shells 35–45 mm. From Taylor (1914). • Monacha cartusiana shells (L.W.). HELICIDAE. Monacha cartusiana (Müller), "Carthusian Snail", "Chartreuse Snail" (formerly Helix cantiana). Ewell Down, Kent. April 24th 1944. J. Armitage. • Theba pisana: shell variation (Taylor). THEBA. Theba pisana (Müller), "White Snail" or "Sandhill Snail", shells 16–22 mm. From Taylor (1914). • Theba pisana (L.W.). HELICIDAE. Theba pisana (Müller), “White Snail”, “Sandhill Snail”. Albany, SW Australia (in gardens and on maritime sandhills). • Trichia striolata, shells (L.W.). HELICIDAE. Trichia striolata (C. Pfeiffer), “Strawberry Snail” (a pale-shelled form). Refuse tip, Marple, Cheshire, Oct. 24th 1947 (F. Taylor). • Candidula, Cernuella, Helicella, Helicodonta, Hygromia, Trochoidea (Ellis). HELICIDAE. 1–3, Helicella itala (L.), "Heath Snail", 12–20 mm. 4–6, Cernuella virgata (da Costa), "Striped Snail" or "Zoned Snail", 9–18 mm. 7–9, Candidula gigaxii (L. Pfeiffer), 7–12 mm. 10–12, Candidula intersecta (Poiret), "Wrinkled Snail", 7–12 mm. 13–15, Trochoidea elegans, "Top Snail", 8–10 mm. 16–18, Hygromia limbata, "Hedge Snail", 12–15 mm. 19–21, Helicodonta obvoluta, "Cheese Snail", 11–14 mm. From Ellis (1926), all rendered here to approximately the same scale. • Ashfordia, Perforatella, Ponentina, Trichia (Ellis). HELICIDAE. 22–24, Ashfordia granulata, "Silky Snail", 7–9 mm. 25–27, Perforatella subrufescens (Miller), "Brown Snail", 8–10 mm. 28–30, Ponentina subvirescens, "Green Snail", 5–7 mm. 31–33, Trichia striolata, "Strawberry Snail", 11–15 mm. 34–39, Trichia hispida (L.), "Hairy Snail", 6–10 mm. From Ellis (1926), all rendered here to approximately the same scale. • Helix sens. lat., exemplifying 16 genera (Adams). HELIX sensu stricto. 1, Helix pomatia Linn., "Roman Snail, Edible Snail, Vine Snail, Apple Snail". 2, Helix aspersa Müller, "Garden Snail, Common Snail". MONACHA. 3, Monacha cantiana (Montagu), "Kentish Snail". 4, Monacha cartusiana (Müller), "Carthusian Snail, Chartreuse Snail". TRICHIA. 5, Trichia striolata (Pfeiffer), "Strawberry Snail" (formerly known as Helix rufescens). 6 and 7, Trichia hispida (Linn.), "Hairy Snail". ASHFORDIA. 8, Ashfordia granulata (Alder), "Silky Snail". PONENTINA. 9, Ponentina subvirescens (Bellamy), "Green Snail". PERFORATELLA. 10, Perforatella subrufescens (Miller), "Brown Snail". THEBA. 11, Theba pisana (Müller), "White Snail, Sandhill Snail". CERNUELLA. 12, Cernuella virgata (da Costa), "Striped Snail, Zoned Snail". CANDIDULA. 13, Candidula intersecta (Poiret), "Wrinkled Snail". HELICELLA. 14, Helicella itala (Linn.), "Heath Snail". CEPAEA. 15, Cepaea nemoralis (Linn.), "Grove Snail, Brown-lipped Snail", with a dart. 16, Cepaea hortensis (Müller), "White-lipped Snail", with a dart. ARIANTA. 17, Arianta arbustorum (Linn.), "Copse Snail". HELICIGONA. 18, Helicigona lapicida (Linn.), "Lapidary Snail". HELICODONTA. 19, Helicodonta obvoluta (Müller), "Cheese Snail". TROCHOIDEA. 20, Trochoidea elegans (Gmelin), "Top Snail". COCHLICELLA. 21, Cochlicella acuta (Müller), "Pointed Snail". From Adams (1896). • Courtship in Helix aspersa (Shaw and Nodder, 1790). The 1790 representation by Shaw (from Naturalist’s Miscellany', vol. 1, no. 30) is fanciful, in that each snail posesses a single dart sac, in which the calcareous "love darts" are developed one at a time.
The following quotation is from Alicia M. Cordero (2001, at http://www.ucmp.berkeley.edu/museum/75th/ab8.html)
"Within the reproductive tract of many land snails is a dart apparatus that consists of calcareous darts and often a mucus gland. These darts, commonly referred to as "love darts" are incorporated into the courtship sequence of land snails in various ways. Sometimes the dart is ejected from the "shooter" and pierces the body wall of the "recipient." In other cases the dart is ejected from the "shooter" without entering the body of the "recipient." In some snails the dart is retained by the "shooter" and used to jab the "recipient." Many hypotheses have been presented to explain the evolutionary significance of the dart apparatus: (1) it is a calcium gift used to entice the partner to act as female; (2) it is a calcium gift used to entice the partner to act as male; (3) it is an honest signal of mate quality; (4) it facilitates species recognition; (5) it is a means of transporting chemicals to a potential mate; and (6) it is used to prevent unwanted matings. The occurrence of darts in land snails is widely distributed throughout many taxonomic groups, however, nearly all of the detailed observations of the reproductive behavior of land snails have been made on only two closely related helicoid species, Helix pomatia and Helix aspersa. The behavior of other species is largely unknown, but anecdotal reports show that in some species the dart may be used differently than in Helix. In order to determine the role the dart is playing in reproduction and whether or not it has the same role within different clades, phylogenetic distribution of darts must be known and the behavior of more dart bearing land snails must be investigated.". • Love darts of Arantia, Cepaea, Cernuella, Helicigona, Helix, Theba (Taylor). Love Darts. HELICIDAE. 1, Cernuella virgata, with a section showing the lateral wings. 2, Helicogona lapicida, with section of the lanceolate head. 3, Helix pomatia, sectioned to show the four wings. 4, Cepaea hortensis, sectioned to show the complex wings. 5, Cepaea nemoralis, showing transverse septa joining the four simple wings, and with diagrammatic transverse sections. 6, Helix aspersa. 7, Theba pisana, with a section through the mid-region. 8, Arantia arbustorum, with section through the lenticular head. ZONITIDAE. 9, Zonitoides excavatus, side and front views, and a further enlargement of the tip. From Taylor (1907 & 1914), with approximate dart lengths 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’.
