Shell equivalve. equilateral, large, flat, discoidal, margin irregular in outline. Valves thick, composed of brittle, imbricating lamella- which both include and are overlaid by a thin membranous epidermis, where eroded of a silvery sheen, interior a dark bronze. Perforation in the right valve about 10 mm. in diameter, median and subumbonal, internally with a raised margin, externally excavated as an oblique furrow ascending to the vertex. From the margin of the perforation a suture leads to the anterior extremity of the hinge plate. Byssus a dense bundle of threads about half an inch long. Hinge line about 43 mm. long. Area much eroded above and traversed by about twenty-two narrow ligamental grooves which slightly radiate from above. Externally the hinge gapes when the valves are closed as in Melina. Adductor small, subcircular, about its own breadth below the perforation. Byssal retractor rather larger than the adductor and immediately above it in the left valve. Pallial margin entire, about half an inch within the ventral margin. Height, 120 ; length, 130 mm.