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 ovoidal or ellipsoidal, 30-50 μm long, 15-20 μm wide,
cauda nearly straight or slightly curved, keel reached at the base of the cauda, striae straight,
paramylon bodies disc-shaped with a hole at its center, 1-3 in number
(An Illustrated Guide to Freshwater Zooplankton in Japan, 2000).
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