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:
Maruyama Park, Ageo city, Saitama Pref., Japan, January 29, 2006 by Y. Tsukii