"Shell small, very thin, fragile, discoidal, inequilateral, the anterior portion obliquely advanced, longer than high; hinge straight, 2/3 as long as the shell length. Right valve moderately convex, ornamented with fine, closely set, somewhat elevated, radiating striae which are surmounted by irregularly spaced concentric lamellae; the concentric lamellae stronger and more densely distributed near the margin; the intersecting points of concentric and radiating striae are not nodulated as the incremental lamellae are far stronger than the radii; the anterior ear nearly triangle in outline, longer than high, with weak concentric lines externally; byssal notch narrow; the posterior ear poorly defined, so that the postero-dorsal corner sometimes nearly vertical. Left valve moderately convex and sculptured almost similarly to the right; the concentric lamellae are quite regularly and widely spaced in comparison with another valve; the anterior ear ornamented with minutely scaled radii. External surface pellucid, vitreous with a silvery luster. Interior shining, the external sculptures are observable from the interior." (fide Okutani, 1962) Size: Normal adult size range is 4 to 6 mm.

Found off Aogashima Island, Japan.
Habitat: Deep water, on muddy bottoms.