Family: Unicells or colonies of non-fixed number of cells; cell body variable in shape; one or more chloroplasts variable in shape; a sexual reproduction by autospore (Illustrations of The Japanese Fresh-water Algae, 1977).
Genus: Colonies of 4, 8 or 16 cells; planktonic; body crescent in shape; tapered at both ends; cells attached to each other at dorsal surface; a chloroplast curved plate-like, with a pyrenoid (Guide book to the "Photomicrographs of the Freshwater Algae", 1998).

S. gracile	Selenastrum sp.	Selenastrum sp.