Subgenus: Cell body cylindrical or dumbbell-shaped, dorso-ventrally not compressed, transverse section circular.
Section [ Eudysphinctium ]: Cell body dumbbell-shaped, constriction strong, cell surface smooth, dotted or punctated (Illustrations of The Japanese Fresh-water Algae, 1977).
Species:
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C. zonatum
var. zonatum ?
49 x 23 μm
Omine-numa
Tsukiyono
Gunma, 2003
C. zonatum
var. zonatum ?
49 x 23 μm
Omine-numa
Tsukiyono
Gunma, 2006
C. zonatum
var. zonatum ?
46 x 32 μm
Omine-numa 6
Minakami
Gunma, 2007
C. zonatum
var. zonatum ?
μm
Omine-numa 5
Minakami
Gunma, 2008
C. zonatum
var. zonatum ?
μm
Kareki-numa
Nikko
Tochigi, 2008
C. zonatum
var. zonatum ?
50 x 23.5 μm
Ichinose-enchi
Norikura highland
Nagano, 2006