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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 (the operculum horny, with spiral growth lines); rising-spiral; 4–8 whorled (?); typically dextral; 1.7–2 mm in its maximum dimension (Paludinella), or 4–6 mm in its maximum dimension (Assiminea); higher than wide; 1.7–2 mm high (Paludinella), or 4–6 mm high (Assiminea); about 1.5–1.8 mm wide (Paludinella), or 2.6–3.9 mm wide (Assiminea); height about 1.2 x the width (Paludinella), or 1.6 x the width (Assiminea); with the body whorl predominating and the spire small and short (Paludinella), or high-spired and tapered gradually from the body whorl (Assiminea). The height of the spire about 0.23 x that of the shell (Paludinella), or 0.38 x that of the shell (Assiminea). The spire acute (in A. grayana), or obtuse (in Paludinella). The shell shortly turretiform (i.e., conical, in A. grayana), or inverted-pyriform (in Paludinella); shallowly sutured (in A. grayana), or deeply sutured (in Paludinella). The whorls neither shouldered nor keeled. The aperture with neither teeth nor calluses. The shell without an umbilicus. The shell thick-lipped; opaque; plain.
General biology, ecology. Terrestrial, or semi-marine. Breathing air directly via the lung-like mantle cavity. Coastal, found in shingle and plant dèbris around the high tide mark, sometimes submerged in brackish water, but more terrestrial than aquatic.
The individuals either male or female (not hermaphrodite).
Classification. Gastropoda; Prosobranchia.
Representation in Britain and Ireland. Assiminea (1, “Dun Sentinel”), Paludinella (1).
Illustrations. • Assiminea grayana, living animal (Reeve). ASSIMINEIDAE. Assiminea grayana Fleming, "Dun Sentinel Snail". From Reeve (1863), with approximate scale added. • Assiminea grayana shell (Ellis). ASSIMINEIDAE. Assiminea grayana Fleming, "Dun Sentinel Snail", shell 4–6 mm. Woolwich. From Ellis (1926).
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’.
