Lamarck, 1818
Description (shell):
Shell thin and brittle, very elongate, oval, shaped rather like a date; umbones close to anterior margin. Sculpture of numerous fine concentric ridges, prominent anteriorly where they may be raised and corrugated, forming flat scales; radiating ridges also present, developed anteriorly into about ten raised ribs. Left valve with three cardinal teeth, the centre one bifid; right valve with two cardinal teeth, the posterior bifid. Adductor scars and pallial line distinct, pallial sinus deep, U-shaped, extending to midline of shell, anterior ribs visible as light grooves, anterior margin crenulate (P. pholadiformis-drawing).
Size:
Up to 60 mm long.
Colour:
Dull white or fawn, with brown or greyish periostracum. Inner surfaces glossy white.
Habitat:
Boring into clay, peat, or soft rocks, this species ranges from the middle shore into the shallow sublittoral.
Distribution:
Distributed from southern Norway to the Mediterranean and West Africa (Distr. P. pholadiformis).