Genus: Colonies of a fixed number of cells, flat, circular in shape; cell body polygonal in shape,
with horn-like projections; cell wall garanulated, wrinkled or notched;
chloroplasts plate-like or reticular; asexual reproduction by zoospore; sexual reproduction by isogametes
(Illustrations of The Japanese Fresh-water Algae, 1977).
Species: Colonies of 8, 16, 32, 64 cells, without perforations; basal parts of the marginal cells polygonal, usually 4- to 5-sides; outer sides concave, incision V- or U-shaped, with two conical processes; cell wall with irregularly reticulate ridge (Photomicrographs of the Freshwater Algae, vol. 18, 1997).