Shell posteriorly rounded or blunt, without sculpture. Hinge margin short, in front of the umbones with few small teeth. Type Malletia chilensis.

Shell large, ovate, moderately inflated, inequilateral, fragile, elongate, equivalve. Periostracum thin, polished. Sculpture absent or feeble commarginal lirae. Lunule and escutcheon absent. Hinge plate weak, with taxodont dentition in two series, separated by a gap. Ligament opisthodetic, external in groove. Pallial line weak; sinus deep.
Nearly the entire group consists of deep-water dwellers in soft sediments, cosmopolitan in distribution and known from the Cretaceous. The northeastern Pacific representatives have been placed in three subgenera, but the definitions of these are so overlapping that we have placed them together again. The origin of the genus name is unknown, but may be derived from the Latin malleatus, hammered; the gender is feminine.