Genus: Unicellular, within a large spherical sheath; two equal-length flagella emerging from anterior end;
cell body spherical or ellipsoidal, connected with gelatinous sheath by fine filaments;
a single chloroplast cup-shaped, with several pyrenoids
(Guide book to the "Photomicrographs of the Freshwater Algae", 1998).
Species: Cell body ovoid or spherical, 40-50 μm in diam.; with many pyrenoids (Illustrations of The Japanese Fresh-water Algae, 1977).