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 μm long, μm wide,
x 640, near Yanase river, Mizuko, Fujimi city, Saitama Pref., Japan, December 2003 by Y. Tsukii
94 μm; x 640