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:

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P. raciborskii 35 x μm Sue-machi Fukuoka, 2001

P. raciborskii μm Hazama marsh Ashikaga Tochigi, 2003

P. raciborskii 37 x μm water reservoir near Yamaguchi Univ. Yamaguchi, 2004

P. raciborskii ? 36 x 20 μm water reservoir near Yamaguchi Univ. Yamaguchi, 2004

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