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 41 μm long, 31 μm wide,
x 640, Okubo Ryoke (picnic-no-mori), Akigase park, Saitama city, Saitama Pref., Japan, February 27, 2005 by Y. Tsukii
94 μm; x 640