Order & Family: Floating unicells or a colony embedded in a matrix;
no differentiation of apical and base structures; only one family.
Genus: Colonies consiting of orderly arranged cells; diameter of cells at transverse section is the same as its length (Illustrations of The Japanese Fresh-water Algae, 1977). Colonies plate-like, cells regularly arranged in a gelatinous matrix; cells spherical or ellipsoid, hemispherical after division (Photomicrographs of the Freshwater Algae, vol. 2, 1984).
Species: Cell body pale blue-green, 1.3-2 (-3) μm in diam. (Photomicrographs of the Freshwater Algae, vol. 2, 1984).