Genus: Unicellular; variable in shape; a constriction at the center of the cell body; mostly longer than wide; flattened; each semicell hemispherical, spherical, ellipsoidal, rectangular, pyramidal or kidney-shaped; no apical indentation.
Subgenus: Cell body flat with strong constriction at center.
Section [ Cyclidium ]: Cell surface smooth or dotted or punctated; semicells half circle, half ellipsoid (Illustrations of The Japanese Fresh-water Algae, 1977).
Species: Cell body medium in size, elliptical hexagon, slightly longer than width, (48-56)-60 μm long, (39-48)-50 μm wide, isthmus 14-17 μm wide; semicells semicircular with flattened apex or trapezoid, both sides wavy (about 8 waves), apex flat or slightly convex, side view broad ovoid (Illustrations of The Japanese Fresh-water Algae, 1977).
C. obtusatum ?
34 x 27 μm
USA, 1999
