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 paradoxum Schilling 1891 ?,
cell body 31 μm long, 24 μm wide,
x 640, Shimo-no-koike (pond), Shiga highland, Yamanouchi town, Nagano Pref., Japan, June 19, 2005 by Y. Tsukii
94 μm; x 640