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:
Phacus landekiensis Stawinski,
cell body 71 μm long (including tail), 43 μm wide,
x 640, near Kejo-numa, Furukawa city, Miyagi Pref., Japan, November 2003 by Y. Tsukii
31 μm
63 μm
94 μm; x 640
Phacus curvicauda Swirenko:
Cell body 24-26 μm diam.,
(25)-38-30 μm long;
2 paramylons
(Illustrations of The Japanese Fresh-water Algae, 1977).