Shell medium-sized to large, inequivalve, inequilateral, irregular, usually with a lamellar sculpture; left valve attached to substract; chomata vermicular, clustered around the ligament; muscular print slightly dorsal.
 

Shell irregular, with a lamellar surface; left valve convex, right valve flat to concave. In this genus, the chomata « retain the interloccking ridge and groove, with large, adjacent anachomata (pustules) along the ridge, fitting into catachomata (pits) in the groove. » – H. H. Harry: “Homology of the five types of marginal denticles (chomata) of living oysters”, American malacological bulletin vol.I, 1983, p.90.