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).
Images of collecting locality:
No.4, Iyari marsh, Omachi city, Nagano Pref., Japan, June 4, 2007 by Y. Tsukii