Tapes decussata

(Linné, 1758)

Description (shell):
Shell broadly oval to quadrate, umbones distinctly anterior; posterior hinge line straight, posterior margin truncate, anterior hinge line grading into the down-sloping anterior margin. Sculpture of fine concentric striae and bolder radiating lines; prominent posteriorly, where the shell is conspicuously decussate. Growth stages clear. Lunule and escutcheon poorly defined. Each valve with three cardinal teeth: centre one in left valve, and centre and posterior in right are bifid. Pallial line and adductor scars distinct. Pallial sinus U-shaped, not extending beyond midline of shell, but reaching a point below the posterior part of the ligament. Lower limb of sinus distinct from pallial line for the whole of its length (T. decussata).

Up to 75 mm long.

Cream, yellowish, or light brown, often with darker markings. Inner surfaces glossy white, often with yellow or orange tints, and with a bluish tinge along dorsal edge (T. decussata-drawing).

Colour cream or grey, its mantle-edges scalloped or edged with white. The siphons are separate throughout their length and fringed with brown at the orifices.

Lower shore and shallow sublittoral, in sand, muddy gravel, or clay.

Patchily distributed in the North Sea (Distr. T. decussata). Distributed south to the Mediterranean and West Africa.