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 (Illustrations of The Japanese Fresh-water Algae, 1977). Species: Cell body 15-(18-32)-34 μm long, 11.5-(12.6-22.4)-23 μm wide, L/W=1.5, isthmus 2.8-8 μm wide, semicells half-ellipsoidal or rounded pyramidal, apices slightly depressed, cell wall with a small number of dots; a single chloroplast with a pyrenoid in each semicell (Illustrations of The Japanese Fresh-water Algae, 1977).

Similar species -- >> C. granatum;

31 μm 63 μm 94 μm; x 640

Images of collecting locality: Ho-daisan-koen (park), Ho, Yoshikawa city, Saitama Pref., Japan, April 9, 2006 by Y. Tsukii