Species [var. macilentum ]: Cell body large, elongated, both side nearly straight at central region, slightly tapered and curved toward ends, 260-(432-678)-800 μm long, 11-(14-21)-25 μm wide, L/W=25-40; cell wall smooth, transparent, bands present; 6-15 pyrenoids in each semicell. [ var. japonicum ]: Cell body wider at the center and narrower at ends than var. macilentum, 400-(447-5780-600 μm long, 23-(32-34) μm wide, L/W=12-18; cell wall finely striated (Illustrations of The Japanese Fresh-water Algae, 1977).

50 μm 100 μm 150 μm; x 400 : 31 μm 63 μm 94 μm; x 640