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: 120-170 μm long, 45-70 μm wide; usually slightly twisted; a long caudal prolongation; flagellum about 1/2 body length; stigma prominent; a discoidal paramylon (paramylum) body central; pellicle longitudinally striated (Kudo, 1966).
var. longicauda: cell body 85-170 μm long, 45-70 μm wide; locomotive flagellum shorter than the cell body; a single paramylon body ring shaped (An Illustrated Guide to Freshwater Zooplankton in Japan, 2000).
Images of collecting locality:
a pond at Izumo Shrine, Izumo city, Shimane Pref., Japan, September 22, 2006 by Y. Tsukii