Parvicardium exiguum

(Gmelin, 1791)

Description (shell):
Shell thick, obliquely oval, hinge line sloping strongly to anterior, umbones well in front of midline. Up to 22 broad ribs, with well-marked concentric ridges between; small tubercle-like spines present on all ribs in young specimens, later persisting only at anterior and posterior margins, and sparingly ventrally. Growth stages distinct. Each valve with two small cardinal teeth; right valve with two anterior and one posterior lateral teeth, the upper anterior being very small. Left valve with single anterior and posterior laterals, the anterior being more prominent. Ribs developed as deep marginal crenulations, not extending into the interior. Adductor scars and pallial line clear (P. exiguum-drawing).

Up to 13 mm long.

Yellowish white, with a thick, patchy brown periostracum. Inner surfaces dull white, or tinted light brown or green.

The gills are long and much folded back. The siphons are rather long, the foot large, long and cylindrical; the mantle margins jagged.

In sand, gravel, or mud; from lower shore into the shallow sublittoral, often extending into estuaries.

Distributed from Norway to the Mediterranean and Black Sea (Distr. P. exiguum).