"Shell small, equivalved, compressée lenticular, both valves being equally convex, ovately subcircular in outline apart from the ears and rather oblique; valves extremely thin and fragile, translucent and almost transparent, pale horn color with a slightly yellowish hue. Beaks placed a little behind the midlength; hinge line straight and very long; ears unequal in size, the posterior pair, which are much smaller than the anterior, alike, îndistinctly defined and merging gradually and imperceptibly into the gênerai convexity and marginal contour of that side of each valve; anterior ears large, subtriangular, prolonged laterally and longer than high, distinctly defined, that of the left valve somewhat convex in outline above and concave below, that of the right valve with a deep and acutely angular byssal sinus at its base. Surface marked by densely crowded and exceedingly minute, irregular and rarely continuous, but on the whole radiating, simple or bifurcating raised Unes, also by comparatively large, regularly disposed and distant squamose radii. In the center of each valve the minute and non-squamose raised lines are essentially parallel to the larger squamose radii, but on the sides the former are disposed obliquely to the latter. The surface of the anterior ear of each pair is minutely cancellated with extremely minute raised lines, which are almost parallel to the hinge line, in addition to the coarser cross lines. The whole sculpture of the exterior of the test is far too minute to be clearly seen without the aid of a microscope or powerful simple lens, but under either of thèse a few faint concentric lines of growth are also visible." (fide Whiteaves, 1893)Size: Normal adult size range is 8 to 12 mm.

From northern Japan to the Bering Sea and down to Guaymas, Mexico including the Gulf of California.
Habitat: Littoral zone to deep water on muddy or sandy bottoms.