Genus: Colonies of a fixed number of cells, flat, circular in shape; cell body polygonal in shape, with horn-like projections; cell wall garanulated, wrinkled or notched; chloroplasts plate-like or reticular; asexual reproduction by zoospore; sexual reproduction by isogametes (Illustrations of The Japanese Fresh-water Algae, 1977).
Species: Colonies of 16, 32, 64 cells, circlar to ovoid in shape with small intercellular space; marginal cells with two low triangular processes forming a broad V-shaped depression outside; processes of neighbouring marginal cells almost attached together; inner cells broad H-shaped, concaved at both sides; cell wall densely granulated (Photomicrographs of the fresh-water algae, 1988).
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Similar species -->> P. duplex
var. angertiniense ?
16 = 10+5+1