Inequivalve, the right valve more ventricose than the left, oval, slightly gaping at both ends, subequilateral, very thin, fragile, subtranslucent, dull white; sculpture of irregular growth lines; anterior side slightly longer, rounded; posterior side rostrated and truncated; dorsal margin straight, almost horizontal on each side of the umbo; ventral margin arcuate and slightly sinuate behind; from the umbo, an oblique ridge to the base of the anterior margin, and another, broader, to the base of the posterior margin; umbos prominent, a little posterior, fissured, the fissure closed up on the inside; right umbo rounded, swollen, a little projecting upon the left valve; hinge edentulous, in each valve a spoon-shaped vertical and strongly buttressed resilifer, the resilium stout, extending to the margin of the valves and uniting them; ligament absent; interior white, slightly nacreous; margins smooth, sharp; pallial sinus moderately deep, rather narrow. Length 73 mm., height 48 mm., section 29 mm. Type locality: Spencer Gulf.