Thyasira croulinensis

(Jeffreys, 1847)

Description (shell):
Shell is fragile, equivalve and equilateral, beaks in the midline, directed inwards. Almost circular in outline, the posterior margin slightly undulating. Ligament is inset. Lunule is inconspicuous; escutcheon is elongate, elevated (T. croulinensis). Sculpture of fine concentric lines. Growth stages are inconspicuous. Hinge line is without teeth. Inside of shell scars are indistinct.

Up to 32 mm in length.

White in colour. Periostracum is slight. Inside of shell is white.

The thickened margin of the mantle is open all round and not prolonged into siphons. The long slender foot is almost cylindrical.

In sandy mud offshore from 7.3-146.3 m.

Has been in the northern North Sea (Distr. T. croulinensis). It is distributed from west Greenland, Spitzbergen, the Murman Coast and northern Norway south to the Mediterranean, the Canary Isles, the Azores and to New England.