"The shell a little higher than long, irregularly suborbicular, with the anterior and lower margins forming together a semicircle and the posterior margin slightly arched or almost straight, compressed, the right valve flatter than the left, translucent silvery white. The valves very thin, fragile, with concentric folds, to the number of about 12 in the adult, broad in the middle of the shell, narrowing towards the lateral margins, with numerous fine, elevated, radiating striae. The auricles small, unequal, the posterior the smallest, faintly marked off from the shell, the anterior distinctly marked off from the shell, the left triangular, the right with an acutely angulated sinus for the byssus. Hinge-margin straight, pit for the cartilage very small, triangular; the internal surface shining." {fide Jensen, 1904)
Size: Normal adult size range is 25 to 30 mm.
Distribution: From the North Atlantic and Arctic Oceans.
Habitat: Deep water, on muddy bottoms.