Genus: Highly flattened; pellicle firm; body form constant (Kudo, 1966). Chloroplasts small, discoid, pyrenoids usually absent; most species flat and leaf-shaped; often with ridges or fins running helically or longitudinally (Illustrated Guide, 1985). Species: Cell body broad ovoidal or nearly circular, broad longitudinal furrow present, 13-20 (-23) μm long, 12-15 μm wide; anterior broadly rounded, posterior slightly pointed; pellicle with longitudinal striae; 1-2 paramylon bodies disc-shaped (Photomicrographs of the Freshwater Algae, 1995).

31 μm 63 μm 94 μm; x 640