Mysia undata

(Pennant, 1777)

Description (shell):
Shell thin and brittle, almost circular, umbones just anterior to midline. Sculpture of fine, closely spaced, concentric lines; growth stages clear. Lunule and escutcheon scarcely evident. Adductor scars and pallial line distinct; pallial sinus U-shaped, extending anterio-dorsally into anterior half of shell. Left valve with three cardinal teeth, the centre one bifid; right valve with two cardinal teeth, the posterior may be bifid (M. undata-drawing).

Up to 38 mm long.

White or light yellow, periostracum indistinct. Inner surfaces glossy white.

The mantle margin is wavy or uneven, but neither fringed nor toothed. The orange siphons are widely separate, protruding from the lower margin and the lower siphon is longer than the upper, while both are fringed.

Burrowing in muddy, coarse bottoms. Offshore, but probably extending little deeper than 50 m.

Distributed from Norway to the Mediterranean and the Canary Isles (Distr. M. undata).