Winckworth, 1930
Description (shell):
Shell thin and fragile, oval to subtriangular; umbones anterior to midline, hinge sloping steeply to anterior. Sculpture of very fine concentric lines, becoming coarser and somewhat corrugated towards margins. Growth stages clear. Right valve with a single small cardinal tooth, adjacent to a triangular plate supporting the external ligament; left valve without teeth, but with hinge line posterior to umbones broad and thickened to support the ligament. Adductor scars and pallial line indistinct, pallial sinus very small (S. jeffreysi-drawing).
Size:
Up to 10 mm long.
Colour:
Outer and inner surfaces white.
Habitat:
In mixed soft substrata, offshore.
Distribution:
Distributed from southern Iceland and Norway to the Mediterranean and Canary Isles (Distr. S. jeffreysi).