Genus: Unicellular, planktonic; cell body flat tri- or quadrangular in shape, with hairy projections at each point;
a single chloroplast plate-like in shape, with a pyrenoid
(Illustrations of The Japanese Fresh-water Algae, 1977).
Similar genus -->> Tetraedron; Pseudopolyedriopsis; Polyedriopsis sp.,
cell body 23 μm long,
x 400, x 640, October 1999, Shirakawa, Fukushima Pref., collected by H. Shiomizu, photo by Y. Tsukii