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. ??, semicell 49 μm long, 52 μm wide, L/W=, isthmus 14 μm wide, x 640, No. 5-2, Mida-ga-hara (bog/marsh), Gassan (mountain), Tsuruoka city (formerly Haguro town) & Shonai town (formerly Tachikawa town), Yamagata Pref., Japan, August 3, 2006 by Y. Tsukii
31 μm 63 μm 94 μm; x 640

Images of collecting locality: No. 5, Mida-ga-hara (bog/marsh), Gassan (mountain), Tsuruoka city (formerly Haguro town) & Shonai town (formerly Tachikawa town), Yamagata Pref., Japan, August 3, 2006 by Y. Tsukii