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| The families of non-marine molluscs of Britain and Ireland (slugs, snails and mussels) |
Morphology. Mussels, enclosed by a hinged, bivalve shell.
Eyes absent (the animal with no head). Without a byssus.
The shell breadth 90–170 mm in its maximum dimension; 90–170 mm wide (and about half as long across the shell from the hinge). The shell oblong, with the margin opposite the hinge more or less straight or only slightly incurved. The shell opaque (and robust); dull black, the interior pearly white or pinkish. The shells dull black, the interior pearly white or pinkish.
General biology, ecology. Freshwater aquatic. Breathing via complex gills. Restricted to clean, cool, fast-flowing rivers and streams at higher elevations, on sandy, gravelly or pebbly substrates; burrowing into interstices in the substrate.
Classification. Bivalvia.
Representation in Britain and Ireland. Margaritifera (1, “Freshwater or Scottish Pearl Mussel”).
Illustrations. • Margaritifera margaritifer, with other Bivalvia (Adams). SPHAERIIDAE. 1, Sphaerium corneum (Linn.), "Horny Orb Mussel"; 2, Sphaerium rivicola (Lamarck), "Nut Orb Mussel, River Orb Mussel". 3, Musculium transversum (Say), "Oblong Orb Mussel"; 4, Musculium lacustre (Müller), "Lake Orb Mussel, Capped Orb Mussel". 5, Pisidium amnicum (Müller), "River Pea Shell, Giant Pea Shell"; 6, Pisidium pulchellum Jenyns; 7, Pisidium obtusale (Lamarck); 8, Pisidium nitidum Jenyns; 9, Pisidium milium Held, "Rosy Pea Shell". UNIONIDAE. 10, Unio tumidus Philipsson, "Swollen River Mussel:; 11, Unio pictorum (Linn.), "Painter's Mussel". MARGARITIFERIDAE. 12, Margaritifera margaritifera (Linn.), "Freshwater Pearl Mussel, Scottish Pearl Mussel". From Adams (1896).
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’.
