Shell thin, elongate, more than twice as long as broad. Umbones anterior to midline; anterior hinge line forming a smooth continuous curve with anterior margin, posterior hinge line sloping more steeply, forming a sharp angle with truncate posterior margin. A distinct keel extends posteriorly from the umbone to postero-ventral corner of each valve. Sculpture of numerous, fine concentric grooves, growth stages clear. Right valve with two cardinal teeth, the anterior grooved, posterior distinctly bifid; left valve with a large, bifid anterior cardinal, and a slender posterior cardinal. Adductor scars and pallial line distinct, cruciform muscle scars unclear. Pallial sinus deep, U-shaped, its lower edge largely fused with the pallial line (G. fervensis-drawing).
Up to 50 mm long.
Dull white, yellowish, fawn, or shades of red, pink, or purple; usually in concentric bands of different intensity, with a few white or cream rays radiating from umbones. Periostracum light or dark brown, persisting as a coarse band around margins. Inner surfaces glossy, white tinted with pink or purple.
Burrows with the large foot usually extended as well as the long and sepatate siphons. Mantle-edges are fringed.
In mixed sand or gravelly bottoms, from the lower shore downwards.
Distributed from Norway to the Mediterranean and West Africa (Distr. G. fervensis).