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 Eudysphinctium: Cell body dumbbell-shaped, constriction strong, cell surface smooth, dotted or punctated 
Cosmarium sp.
1 sample
86 x 60 μm
Univ. A.V.M.
Obihiro
Hokkaido, 2005
C. moniliforme
10 samples
16-40 μm
1998-2008
Cosmarium sp.
C. moniliforme ?
1 sample
31 x 19 μm
Imou bog
Toyohashi
Aichi, 2004
C. zonatum
6 samples
49-50 x 23 μm
2003-2008
C. turgidum
= Actinotaenium
3 samples
198-214 μm
2004-2005
C. connatum
16 samples
67-75 x 49-53 μm
2003-2008
