Genus: Cingulum (horizontal groove) located at the center of the body
(Illustrations of The Japanese Fresh-water Algae, 1977).
Cingulum more or less median; sulcus straight (Illrustrated Guide, 1985).
Gymnodinium sp. ?,
cell body 25 μm long, 21 μm wide,
x 640, Komado marsh (or bog), Showa village and Tajima town, Fukushima Pref., Japan, August 22, 2004, by Y. Tsukii
94 μm; x 640