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 [Eucosmarium]: Cell body dorso-ventrally compressed, with strong constriction at the center, transverse section elliptical or diamond-shaped.
Section [Pyramidatae]: Cell surface smooth; semicells pyramidal with flattened apex or trapezoid (Illustrations of The Japanese Fresh-water Algae, 1977).
Species:

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Apex flatted, semicell scalariform
C. trilobulatum 35 x 23 μm Omine-numa Tsukiyono Gunma, 2003

Similar species -- >> C. hammeri; C. pseudopyramidatum v. varniolicium; C. nymannianum;

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