Several variously preserved shells are in hand, characterized by 1) subcylindrical, slender and somewhat constricted medially, involute shell attaining 2.8 mm in height, 2) spire sunken in the deep and narrow adapical umbilicus bounded by the rounded edge of the body whorl, 3) aperture as high as the total height, very narrow in the adapical two-thirds and with prominent, narrowly arched upper rim, widening and drop-shaped abapically; columella short, somewhat revolute, 4) sculpture of fine collabral riblets crossed by even, shallowly incised spiral lines. Compared to the figure published by LIN GUANG-YU & Qi ZHONG-YAN (1985: Fig. 2 I) and referred to as Retusa (Coelophysis) elegantissima Habe, 1950, the Thai shells appear to be more constricted medially and have the aperture wider and less expanded abapically. Retusa elegantissima Habe, 1950, differs in having a distinctly cylindrical shell not constricted at all. Retusa lineolata Yokoyama, 1924, is readily distinguished in having a markedly stouter shell. The Indian Ocean Retusa sp. figured by BOSCH et al. (1995) is also closely related, but exhibits a stouter shell with spiral threads instead of grooves.
DISTRIBUTION AND HABITAT. The species is distributed in the tropical Indo-West Pacific and northward to Japan. It dwells in sandy mud, from 10 to 50 m depth (HORI in OKUTANI, 2000).
FOSSIL RECORDS. Pleistocene of Japan.