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 8-32 (rarely 4, 64 or 128 cells) with large intercellular space; inner cells H-shaped, trapezoid to rectangular when matured; outer half of the marginal cells prolonged into two horn-like processes with a tuft of long bristles; daughter colonies formed in a vesicle released from mother cell; cell wall smooth (Photomicrographs of the fresh-water algae, 1994).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: No.1, Kejo-numa, Furukawa-Ono, Osaki city (formerly Furukawa city), Miyagi Pref., Japan, October 29, 2006 by Y. Tsukii