Valves elongate-rectangular, with sub-parallel dorsal and ventral margins and a slightly concave posterodorsal margin giving a triangular posterior termination in lateral view. Fossae deep, slit-like, becoming more equidimensional towards the anterior and posterior margins. Sexual dimorphism conspicuous; males proportionally slimmer both in lateral and dorsal view, and with a compressed posteroventral marginal area in both valves. Distal process of male copulatory appendage subtriangular with a produced, curled, posterior free corner and an elongate lamellar extension on the distal (anterior) free corner.
A sublittoral species living at depths down to 75 metres.
Neale (1973) has given a thorough review of both recent and fossil records of this species, and subsequently (1975) published further illustrations of valves and appendages.
Found most commonly in the northern part of the British Isles; according to Neale (1975) it is widely distributed from Shetland and S Norway to the Bay of Biscay. It does not live in the Mediterranean.