Species [ var. connatum ]: Cell body 22-24 μm long, 19.6-25 μm wide (excluding spines), isthmus 7-9 μm wide; spines short; semicells inverted semicircle in shape, apex flat or slightly convex. [ var. pseudamericanum Grönblad ]: Cell body larger than v. connatum 39-45 μm long, 25-36.45 μm wide (excluding spines), isthmus 5.6-11 μm wide; corners of semicells protruded upward making its apex concave. [ var. rectangulum Roy et Bisset ]: Cell body 14-20 μm long, 14.7-20 μm wide (without spines), isthmus 3.5-5.6 μm wide; side margins of semicells not convex; spines longer and thicker than v. connatum (Illustrations of The Japanese Fresh-water Algae, 1977)

31 μm 63 μm 94 μm; x 640

Staurastrum connatum var rectangulum ??, cell body 19 μm long, 18 μm wide, L/W=1.1 (excluding spines, 3.5 μm), isthmus 5 μm wide, x 640, Maimeno-ike (pond), Norikura highland, Azumi, Matsumoto city (formerly Azumi village), Nagano Pref., Japan, June 8, 2006 by Y. Tsukii
31 μm 63 μm 94 μm; x 640

Images of collecting locality: Maimeno-ike (pond), Norikura highland, Azumi, Matsumoto city (formerly Azumi village), Nagano Pref., Japan, June 8, 2006 by Y. Tsukii