Subgenus: Dysphinctium
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 cylindrical or dumbbell-shaped, dorso-ventrally not compressed, transverse section circular (Illustrations of The Japanese Fresh-water Algae, 1977).
Section Calocylindrus: Cell body cylindrical, slightly constricted at the center, cell surface granulated or with knobs 
C. nipponicum
37 x 17 μm
Omine numa
Tsukiyono
Gunma, 2003
C. nipponicum
37 x 21 μm
Koigakubo marsh
Tessei-cho
Okayama, 2004
C. amoenum
10 samples
39-50 x μm
2003-2008
C. elegantissimum
2 samples
61 x 26 μm
2006-2007
