Genus: Colonies spherical, with inner empty space; cells attached to each other by a protrusion of cell wall, arranged in a single layer; cell body mostly spherical with some conical or grobular bulges; chloroplasts cup-shaped with a pyrenoid; reproduction by asexual coenobium (Illustrations of The Japanese Fresh-water Algae, 1977). Species: Colonies of 8, 16, 32 or 64 cells, up to 100 μm in diam.; cell body spherical, with a small wart-like process, up to 15 μm in diam.; cells connected to adjacent cells by 1-3 strands; a single chloroplast parietal, plate-like, with a pyrenoid (Photomicrographs of the Freshwater Algae, vol. 8, 1988).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: O-ike, Shiroyama Park, Okegawa city, Saitama Pref., Japan, January 29, 2006 by Y. Tsukii