Species [ var. laevis ]: Cell body small in size, slightly constricted at the center, (70-120)-145 μm long, 17-(18-32) μm wide, L/W=3-4; semicells tapered from the base to ends, both ends broadly rounded with a deep incision at center; cell wall roughly dotted; lateral view spindle-shaped, tapering stronger than frontal view. [ var. tropicus ]: Larger than var. laevis, 115-(134)-153 μm long, 24-(28) μm wide, L/W=5. (Illustrations of The Japanese Fresh-water Algae, 1977). [var. minutus]: Cell body (37-)45-60(-75) μm long, (12-)17-20 μm wide, L/W=2.8-3.5, (Coesel & Meesters 2007).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: Tanohara marsh, Shiga highland, Yamanouchi town, Nagano Pref., Japan, June 1, 2006 by Y. Tsukii