Gamophyceae: Zygnematales: Desmidiaceae
(Charophyceae: Zygnematales: Desmidiaceae)

Cosmarium

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 (Illustrations of The Japanese Fresh-water Algae, 1977).