(da Costa, 1778)
Description (shell):
Shell solid and equivalve. Almost equilateral, beaks just in front of the midline, directed inwards. Cylindrical in outline with anterior and posterior extremities rounded and gaping widely. Ligament is a dark brown arched band extending one-third the way to the posterior margin. Sculpture of fine concentric lines and ridges. Growth stages are not clear. Right valve with two cardinal teeth, each curling out from beneath the umbo like blunt spines, the posterior the larger. Left valve with one similar cardinal. Cruciform muscle scars are obscure. Pallial sinus is deep, extending to a point below the beaks. Margin is smooth.
Size:
Up to 63.5 mm in length.
Colour:
White or fawn in colour. Periostracum thick, wrinkled, dark brown or greenish yellow. Inside of shell white (S. chamasolen-drawing).
Habitat:
Lives in bottoms of thick, solid, black mud, muddy sand, or muddy gravel, offshore to considerable depths.
Distribution:
Occurs from the Norwegian Sea to the Mediterranean, along the Atlantic coast of Morocco, to the Canary Isles and to just south of the Equator (Distr. S. chamasolen).