The shell is low patelliform, thin, and oval in outline. The width is about 80% and height is about 30% of length, respectively. The surface is white, usually heavily eroded, remaining only the trace of radial and growth lines, but young specimens exhibit very fine, crowded, white radiating threads that are crossed by concentric growth lines.
The internal surface is white and smooth, with a low, thick ridge running along the mantle edge. This ridge exhibits an opaque ring . The marginal area, a broad prismatic region, outside of the above-mentioned ring, is translucently white with traces of white radial lines. The central part, within the muscle scar, has a microscopic vermicular surface.
The radula is docoglossate. The central tooth is absent, but present a ridge-like structure in the center. The lateral tooth is trilobate distally and has a long shaft with a deep longitudinal groove inside. The innermost ramus is skinny with a sharp tip, the central one is broadly triangular, and the outermost one is quadrate in outline.
Measurements'. Holotype (NSMT Mo-69970) length 17.1 mm, width 15.0 mm, height 4.5 mm; Paratype (NSMT Mo-69971) 16.0X 14.9x4.4 mm.
Remarks: This is the second species of the genus Bathyacmaea established in 1992 on the basis of B. nipponica OKUTANI, TSUCHIDA and FUJIKURA from the seep area in Sagami Bay. This genus is characterized by trifid lateral tooth. The occurrence of congeneric species from chemosynthetic communities from the southwestern Japan is most interesting.
This species is characterized by broad foliated layer extending far beyond the crossed lamellar layer which represents an opaque ring inside.
Distribution: Minami Ensei Knoll, 700 m deep (type locality) and Iheya Ridge, 1380 m deep.