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, L/W=,
x 640, used waterfield near Karakemi marsh (Yasaka village), Matsuzaki, Omachi city, Nagano Pref., Japan, April 24, 2005 by Y. Tsukii
94 μm; x 640
Cell body 26 μm long, 24 μm wide, L/W=, x 640