Family: Unicells or cells loosely attached forming hyphae; cell body varied in shape, a constriction at the center in most species; cell walls consisting of two or more parts, with small pores and various ornaments (Illustrations of The Japanese Fresh-water Algae, 1977).
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).

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Subgenus: Dysphinctium (Cell body cylindrical or dumbbell-shaped, dorso-ventrally not compressed , transverse section circular)
Actinotaenium: Cell body cylindrical, slightly constricted at the center, cell surface smooth or dotted or punctated		Calocylindrus: Cell body cylindrical, slightly constricted at the center, cell surface granulated or with knobs
Eudysphinctium: Cell body dumbbell-shaped, constriction strong, cell surface smooth, dotted or punctated		Orbiculatae: Cell body dumbbell-shaped, constriction strong, cell surface granulated or with knobs
Subgenus: Eucosmarium (Cell body dorso-ventrally compressed, with strong constriction at the center, transverse section elliptical or diamond-shaped)
Globuliferae: Cell surface smooth or dotted or punctated; semicells circular, ellipsoidal, reniform		Ornatae: Cell surface granulated, gnarled or spiny; semicells circular, ellipsoidal, reniform
Cyclidium: Cell surface smooth or dotted or punctated; semicells half circle, half ellipsoid		Cristatae: Cell surface granulated, gnarled or spiny; semicells semicircular, semi-elliptical
Pyramidatae: Cell surface smooth or dotted or punctated; semicells pyramidal with flattened apex or trapezoid		Margaritiferae: Cell surface granulated, gnarled or spiny; semicells pyramidal with flattened apex or trapezoid
Quadratiformes: Cell surface smooth or dotted or punctated; semicells rectangular		Tetridium: Cell surface granulated, gnarled or spiny; semicells rectangular
Microcosmarium: Cell surface smooth or dotted or punctated; semicells polygonal

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