Species [ var. furcatospermum ]: Cell body 18-(19.6-29) μm long, 16.5-(18-25) μm wide, isthmus 5.6-8.4 μm wide; semicells semicirucular with flattened apex, margins wavy (laterally 4-5 waves, apically 4 waves); two rows of granules radially arranged within the margin; central region smooth (lacks granules or other ornaments). [ var. koreanum Skvortzow ]: 31-32 μm long, 25-28 μm wide, isthmus 8-11 μm wide (Illustrations of The Japanese Fresh-water Algae, 1977).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: Rice field between Kita-Omachi station and Nogu river, Omachi city, Nagano Pref., Japan, June 1, 2008 by Y. Tsukii