Family: Unicells; cell body spherical or broad ellipsoidal; chloroplasts 1 to several in number, cup-shaped or plate-like, reticulated or star-shaped; with or without pyrenoids; reproduction by autospores and zoospores; many species found in soil (Illustrations of The Japanese Fresh-water Algae, 1977).
Genus: Unicellular, planktonic; cell body flat, triangular in shape, each point drawn out (Guide book to the "Photomicrographs of the Freshwater Algae", 1998).
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Similar genus -->> Tetraedron; Tetraedriella (Xanthophyceae);
P. tripus
35 μm
Abiko
Chiba, 2000