Genus: Unicellular, but autospore may become temporary colonical; planktonic; cell body spherical with many elongated spiny projections; a single chloroplast cup-shaped, with a single pyrenoid (Guide book to the "Photomicrographs of the Freshwater Algae", 1998).
Species: Vegetative cells spherical, 8-10 μm diam., with short spines 20-40 μm long, 1 chloroplast cup-shaped, 1 pyrenoid (Illustrations of The Japanese Fresh-water Algae, 1977).