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| The families of non-marine molluscs of Britain and Ireland (slugs, snails and mussels) |
Morphology. Limpets, with a conspicuous, protective patelliform shell bearing only a vestigial spire (the latter represented by a small, rearwardly-directed apical point).
The animal with one pair of tentacles only. Eyes at the bases of the tentacles.
The shell vestigially rising-spiral, or . The animal dextral, with the genital orifice and anus on its right side, although the vestigial spire of the shell inclines to the left. The shell wider than high; 4–7 mm wide (more or less ovoid, and about half this across). The shell very asymmetric about the vertical axis, with the spire much displaced to one side (i.e., taking account of the displaced vestige of the spire). The shell opaque; plain.
General biology, ecology. Freshwater aquatic. The mantle cavity obliterated, and a lobe of the mantle functioning as a gill (and gas exchange also occurring via the skin in general). In clean, still or slow moving water, attaching to plants, submerged timber, or the shells of larger molluscs.
Hermaphrodite (but individuals acting as either male or female when mating).
Classification. Gastropoda; Pulmonata.
Representation in Britain and Ireland. Acroloxus (1, “Lake limpet”).
Illustrations. • Acroloxus lacustris, with Ancylidae and Lymnaeidae (Adams). LYMNAEIDAE. 1, Myxas glutinosa (Müller), "Glutinous Snail". 2, Lymnaea involuta Thomson, probably a form of L. peregra. 3b, Lymnaea peregra (Müller), "Common Pond Snail, Wandering Pond Snail". 3a and 3e, Lymnaea ovata (Draparnaud), probably also a form of L. peregra. 4, Lymnaea auricularia (Linn.), "Ear Pond Snail". 5, Lymnaea stagnalis (Linn.), "Great Pond Snail". 6, Lymnaea palustris (Müller), "Marsh Pond Snail". 7, Lymnaea truncatula (Müller), "Dwarf Pond Snail". 8, Lymnaea glabra (Müller), "Mud Pond Snail". ANCYLIDAE. 9, Ancylus fluviatilis Müller, "River Limpet". ACROLOXIDAE. 10, Acroloxus lacustris (Linn.), "Lake Limpet". From Adams (1896). • Acroloxus lacustris, with Ancylus fluviatilis (Reeve). ANCYLIDAE. 1, Ancylus fluviatilis Müller ("River Limpet"). ACROLOXIDAE. 2, Acroloxus lacustris (L.), "Lake Limpet". 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’.
