Unarmoured marine planktonic dinoflagellate, with a distinctive spiral-shaped cingulum. Is a known red tide species associated with large fish kills and economic loss in Japanese and Korean waters. Cells are oval and slightly flatenned dorso-ventrally. Chains, rarely more than eight cells, are common. An apical groove is present on the apex originating from the anterior end of the cingular and sulcal juncture and extending to hte dorsalside of the epitheca. The epitheca is conical and rounded at the apex. The hypotheca is bilobed. the cingulum is deep and excavated. It is placed about 0.6 times the cell length, and descends in a distinct left-handed spiral of 1.8-1.9 turns around the cell. the narrow and shallow sulcus nearly runs parallel to the cingulum making 0.8-0.9 turns around the cell between the proximal and distal ends of the cingulum. the sulcus deepens and widens towards the antapex and divides the hypotheca into two asymetrical lobes. The right lobe is narrower and slightly longer than the left lobe. Trichocysts have been observed in this species, but the number per cell varies, and not all cells bear them. The presence and number of trichocysts increases with cell and culture size. This is a photosynthetic species with numerous yellowish-green to brown chloroplasts, rod-shaped or ellipsoid in shape. The nucleus is situated anteriorly in the epitheca. A red stigma is present dorsally in the epitheca. 

Body_length: 30-40 µm
Body_Width: 20-30 µm
Bloom: Yes