Genus: Cell body short, radiate in shape; apical view of the cell, triangular, polygonal, ellipsoidal or spindle-shaped; zygospores formed outside of mother cells (Illustrations of The Japanese Fresh-water Algae, 1977) Subgenus: with arm-like projections (Illustrations of The Japanese Fresh-water Algae, 1977) Species:

31 μm 63 μm 94 μm; x 640

Staurastrum biexcavatum Hirano var biexcavatum: Body with arms 40-41 μm long (including arms), 35-38 μm wide (including arms), constriction 8 μm wide; small; body length slightly longer than width; constriction moderate; hemicells V-shaped, with flattened apex and arm-like projections at both edges; the projections tapered, consisting of about 7 segments, 3 spines at terminal (Illustrations of The Japanese Fresh-water Algae, 1977)

Staurastrum biexcavatum var binodulum Hirano: Body with arms 34.4 μm long, 41 μm wide, constriction 65 μm wide; apex of hemicells slightly convex; swells at base of the arm-like projections (Illustrations of The Japanese Fresh-water Algae, 1977)