Shell large, often broad, strongly triangular in shape, with thin and fragile valves; outside made of calcite with spines or spatulae radially arranged; inside made of aragonite with a large and deep posterior adductor muscle scar; hinge devoid of teeth. Ligament running up to the level of the posterior adductor.
 

« Shell reaching large size, up to 480mm (about 19 inches) in length, wedge, wing-shaped to subglobular in outline. Thin to rather heavy in structure and sculptured with spinose to imbricate, sometimes nearly obsolete, radiating ribs. Nacreous layer not divided by a longitudinal sulcus, occupying entire surface of anterior two-thirds to three-fourths of the inner side of valves. The posterior adductor muscle scar located subcentrally. » – J. Rosewater: “The family Pinnidae in the Indo-Pacific”, Indo-Pacific mollusca vol.I n.4, Philadelphia 1961, p.203.
 

« Shell reaching a large size, up to 700mm (about 28 inches) in length in some species; wedge-shaped, generally fragile in structure and sculptured with radiating ribs which may bear spines or imbrications. Nacreous layer divided by a longitudinal sulcus into dorsal and ventral lobes. Posterior adductor muscle scar usually completely enclosed within dorsal lobe. » – J. Rosewater: “The family Pinnidae in the Indo-Pacific”, Indo-Pacific mollusca vol.I n.4, Philadelphia 1961, p.187.