"A small bivalve, rounded in outline, equivalve and equilateral except for ears, and compressed. Shell thin, semitransparent and whitish with hyaline polish; its outer surface apparently smooth but finely striated with many delicate radial ridges crossed by faint sublaminate incremental lines of growth. Radial ridges close-set, measuring about 12-13 in number for a breadth of 1 mm, and sometimes dichotomous here and there. Ears unequal, the anterior larger and a little longer than the posterior. The anterior car of right valve with a deep byssal notch and also that of left valve are provided with many microscopically minute teeth arranged radially." (fide Hiro, 1938) Size: Normal adult size range is 10 to 15 mm.

From Kyushu, Shikoku and Honshu, Japan.
Habitat: Sublittoral zone to deep water, on muddy bottoms.