Shells « small to medium-sized, up to 90 mm. The shells are equivalve or inequivalve, with the right valve larger and overlapping the left. They are thin-walled, and rounded or distorted in shape. The posterior end is either truncated or bluntly rostrate, and the posterior end gapes in some species. The shell is composed of aragonite and exterior sculpture is smooth to granulate, with occasional striations, commarginal ridges, or undulations […] interior shell margins are smooth […] and the anterior adductor muscle is narrower than the posterior. The edentate hinge is either internal or external, with a calcareous ossicle. » (neogeneatlas.net, after Mikkelsen & Biele, 2008).
 

« Shell thin, domed, oval, slightly elongated, inequivalve, the right valve more rounded than the left, inequilateral, with well-marked summits slightly curved forward; hinge dissimilar; on the right valve, a slightly deep angular notch, and in front a narrow nymphal callus for an external ligament corresponding to a spatula or more pronounced prominence, and two oblique folds of the left valve; two small, distant muscle impressions; the anterior very lowered and united to the posterior by an abdominal ligule rather tucked backwards. » – H. M. D. de Blainville: “Mollusques, Mollusca”, Dictionnaire des Sciences Naturelles vol.XXXII, Strasbourg & Paris 1824, p.347.