Genus: Filament without branching; cell body cylindrical; each cell wall consists of two parts with "H" structure overlapping at the midregion; chloroplasts many, disc-shaped, without pyrenoids (Guide book to the "Photomicrographs of the Freshwater Algae", 1998). Species: Filaments with a slight constriction at cell-cell junction; cell body cylindrical, slightly swelled at the center, 10-13 μm long ,4-5 μm wide, L/W=1.5-2-(3); chloroplasts 2 or 3 in number, plate-like (Illustrations of the Japanese Freshwater Algae, 1977). Filaments 4-6 μm wide; cell body up to 2 times longer than its width (Süßwasserflora von Mitteleuropa 3, Xanthophyceae 1, 1978).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: Oyomi marsh, Hakuba village, Nagano Pref., Japan, May 8, 2006 by Y. Tsukii