Subgenus: Entomum (Apical area deeply indented or notched) Section: Incisa (Cell surface smooth; apical area without spiny projections) Species: Cell body 47-73 μm long, 34-36 μm wide, isthmus 11-14 μm wide (Illustrations of The Japanese Fresh-water Algae, 1977).

31 μm 63 μm 94 μm; x 640

Euastrum gnathophorum W. et G.S. West, semicell 33 μm long, 34 μm wide, isthmus ?? μm wide, x 640, Kodanuki marsh, Fujinomiya city, Shizuoka Pref., Japan, April 29, 2006 by Y. Tsukii
31 μm 63 μm 94 μm; x 640

Images of collecting locality: Kodanuki marsh, Fujinomiya city, Shizuoka Pref., Japan, April 29, 2006 by Y. Tsukii

Euastrum gnathophorum Lenormand var. gnathophorum: Cell body 60-74 μm long, 34-46 μm wide, isthmus 8-15 μm wide, (Illustrations of the Fresh-water Algae, 1977).

Euastrum gnathophorum var. germanicum (Raciborski) Lütkemüller: Cell body 59-78 μm long, 36.5-47.6 μm wide, isthmus 7-12.5 μm wide, L/W=1.5-1.75 (Illustrations of the Fresh-water Algae, 1977).