Subgenus [Eucosmarium]: Cell body dorso-ventrally compressed, with strong constriction at the center, transverse section elliptical or diamond-shaped.
Section [ Cyclidium ]: Cell surface smooth; semicells half circle, half ellipsoid (Illustrations of The Japanese Fresh-water Algae, 1977).
Species[ magnum ]: Cell body 78-84 μm long, 78-80 μm wide, isthmus 39-44 μm wide; (Illustrations of The Japanese Fresh-water Algae, 1977).
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Similar species -- >> C. obsoletum; C. ralfsii;
C. taxichondrum
var. magnum
84 x 80 μm
Koigakubo marsh
Tessei-cho
Okayama, 2004
C. taxichondrum
var. magnum
86.5 x 89 μm
Koigakubo marsh
Tessei-cho
Okayama, 2006
C. taxichondrum
var. magnum
100 x 95 μm
Yamamuro m.8
Maibara
Shiga, 2008