Genus: Planktonic; colony of 4 cells; cell body spherical, covered with elongated spiny projections;
cells attached with each other arranging cruciform on a plane, with a small space at the center of the colony;
a single chloroplast plate-like, with a pyrenoid
(Guide book to the "Photomicrographs of the Freshwater Algae", 1998).
Species: Cell body triangular or ovoid; 3-6 μm in diam., colonies of 4 cells arranged in cruciform in a flat plate; small space present or absent at the center of the colony; outer margins of the ccells rounded, with 5-6 short spines; a single chloroplast parietal and laminated, with a pyrenoid (Photomicrographs of the fresh-water algae, 1984).