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 37-68 μm long, 25-45 μm wide,
dorsally broad ovoidal, cauda relatively long and curved, striae straight,
a longitudinal prominent ridge at the center which makes frontal view triangular;
a locomotive flagellum nearly the same as the cell body in length;
paramylon bodies large disc-shaped, 1-2 in number
(An Illustrated Guide to Freshwater Zooplankton in Japan, 2000).
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