« The members of this family are found in muddy sand or gravel at or below low tide mark. They have characteristically rounded shells with forward-facing umbones (projections). The valves are flattened and deeply etched with concentric rings. Each valve bears two cardinal and two plate-like lateral teeth. » (Barrett & Younge, 1964). Some species can also live in much deeper water.
 

« Shell free, bivalve, aequivalve, regular, inequilateral, triangular-circular, closed. Ligament external. On both valves two cardinal teeth, subsimilar, including one bifid per valve: on the right valve the posterior one, on the left valve the anterior. No lateral teeth. Two large muscular impressions; pallial sinus simple. » – H. G. Bronn: Italiens Tertiär-Gebilde und deren organische Einschlüsse, Heidelberg 1831, p.xii.
 

« This genus, established by Daudin, is close to Bucardium by the shape of its hinge but, exteriorly, substantially departs from it. Indeed, the only shell it includes is lengthened, flat, and the valves looks like nails. The two internal muscular prints are very elongated. » – L. A. G. Bosc: Histoire naturelle des coquilles vol.III, Paris 1802, p.76.