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 23 μm long, 19 μm wide,
x 640, Kenmin-kenko-fukushi-mura Park, Koshigaya city, Saitama Pref., Japan, January 29, 2005 by Y. Tsukii
94 μm; x 640