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 aeruginosum Stein 1939 ?,
cell body 24 μm long, 18 μm wide, L/W=,
x 640, Jizoh-bori at Sannoh Park, Saitama city, Saitama Pref., Japan, April 17, 2005 by Y. Tsukii
94 μm; x 640
Cell body 29 μm long, 21 μm wide, L/W=, x 640