(Gmelin, 1791)

Description (shell):
Shell fragile, almost equivalve, with the left valve just a little more convex than the right. Inequilateral, beaks in front of the midline. Approximately oval in outline, with the posterior dorsal line straight and the posterior margin abruptly truncated and gaping. Periostracum often with agglutinated sand grains, echinoderm spines, etc. Ligament is internal, immediately below and behind the beaks, in an elongated, narrow, longitudinal ridge and with an underlying, supporting, white calcareous plate or lithodesma, which is broadest posteriorly. Shell surface with coarse granulations, these gathered into radiating lines some of which are prominent as radiating ribs; also with concentric undulating ridges, which may be pronounced, particularly in smaller shells. Hinge line is without teeth. Inside of shell is glossy, with the external ribbing showing through. Scars are faint, adductors thin, about equal. Pallial sinus is deep, extending beyond the umbones.

Size:
Up to 38.1 mm in length.

Colour:
White in colour, rather translucent. Periostracum light brown. Interior iridescent.

Animal:
The animal is white with a yellowish tinge. The anterior part of the mantle has a slight fringe of a few projecting points. The siphons are short, fringed at their orifices and having a few filaments round the base of each. The white foot is tongue-shaped, extensible and grooved for the production of a byssus (L. norwegica-animal).

Habitat:
Inhabiting sand and silty sand from just offshore to varying depths.

Distribution:
Distributed from Iceland, the Faroes and northern Norway to the Iberian Peninsula, the Atlantic coast of Morocco, Madeira and the Canary Isles (Distr. L. norwegica).

Kingdom Animalia
Phylum Mollusca
Class Bivalvia
Subclass Anomalodesmata
Order Pholadomyoida
Family Lyonsiidae
Genus Lyonsia
Species Lyonsia norwegica

Status in World Register of Marine Species

Accepted name: Lyonsia norwegica (Gmelin, 1791)

Scientific synonyms and common names

Mya norwegica Gmelin, 1791
Mya striata Montagu, 1811
Amphidesma corbuloides Lamarck, 1818
Anatina truncata Lamarck, 1818
Tellina coruscans Scacchi, 1833
Anatina elongata Hanley, 1842
Myatella montagui Brown, 1844
Lyonsia norwegica var. major B.D.D., 1889
Lyonsiella compressa Allen & Turner, 1974

Haas, F., 1926. Lamellibranchia. In Grimpe, G. & Wagner, E.: Die Tierwelt der Nord- und Ostsee.

Jeffreys, J.G., 1869. British conchology. Vol. V -258 pp. Van Voorst, London.

Poppe, G.T. & Y. Goto, 1993. European Seashells. Vol. II. 221 pp. Wiesbaden/Verlag Christa Hemmen.

Seaward, D.R., 1990. Distribution of the marine molluscs of north west Europe. Nature Conservancy Council.

Step, E., 1927. Shell life. 421 pp. Frederick Warne & Co., LTD, London.

Tebble, N., 1966. British Bivalve Seashells. 212 pp. Trustees of The British Museum (Natural history). London.

You can continue searching for Lyonsia norwegica on one of these Web sites:

Fauna Europaea (animals) | IOPI (plants) | NCBI (genetic)

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