Species: Cell body curved in various degree, slightly swells at the center, 90-(117-256)-260 μm long, 14-(19-34)-45 μm wide, L/W=6-8, cell wall smooth, transparent or brownish; chloroplasts with 2-4 laminae; semicells with 4-8 pyrenoids (Illustrations of The Japanese Fresh-water Algae, 1977). Cell body 140-250 μm long, 28-34 μm wide, L/W=5-8; cell wall smooth; chloroplasts with 5-6 laminae; semicells with 3-4 pyrenoids (Photomicrographs of the Freshwater Algae, vol. 1, 1984).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: Tsuki river (exit of drainage ditch), upstream of Yanagimachi bridge, Aoyama/Shimozato, Ogawa town, Saitama Pref., Japan, November 25, 2007 by Y. Tsukii