Subgenus: Entomum (Apical area deeply indented or notched) Section: Incisa (Cell surface smooth; apical area without spiny projections) Species: Cell body 95-132 μm long, 56-70 μm wide, L/W=1.7, isthmus 15.4-22 μm wide; upper lateral lobes mamillate and projected obliquely upward, located slightly anterior from the middle line of semicells; a single pore present at the center of semicells (Illustrations of The Japanese Fresh-water Algae, 1977).

31 μm 63 μm 94 μm; x 640

Euastrum humerosum Ralfs var. ??, cell body 117 μm long, 64 μm wide, L/W=1.8, isthmus 18 μm wide, x 640, Yacho-no-mori marsh (near road sign No. 1), Sukawa highland, Kurikoma mountain, Higashi-naruse village, Akita Pref., Japan, July 24, 2005 by Y. Tsukii
31 μm 63 μm 94 μm; x 640

Cell body 115 μm long, 67 μm wide, L/W=1.7, isthmus 15 μm wide, x 640

Cell body 120 μm long, 66 μm wide, L/W=1.8, isthmus 19 μm wide, x 640