Species [ var. amoenum ]: Cell body cylindroid, 42-67 μm long, (22-28)-30 μm wide, L/W=2, isthmus 13-21 μm wide; cell wall covered with large granules, longitudinally arranging in 7-8 rows forming a cross (+) pattern on the cell wall; 2 pyrenoids in each semicell. [ var. alternans ]: Cell body 44-45 μm long, 23-24 μm wide, isthmus 15.4 μm wide; granules arranging as an "X"-shaped pattern on the cell wall (Illustrations of The Japanese Fresh-water Algae, 1977).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: No.5, Omine-numa (pond/marsh), Omine, Minakami town (formerly Tsukiyono town), Gunma Pref., Japan, October 21, 2007 by Y. Tsukii