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 obovoid to long triangular, slightly twisted; anterior end broadly rounded, sharrowly bilobed; laterally undulated and asymmetrical; posterior end tapered into a long slightly curved cauda, 22-26 μm long, 10-13 μm wide; usually 3 paramylon bodies cup-shaped, parietal plate, two located at the right and left halves of the cell at the anterior end, remaining one at the posterior half of the cell (Photomicrographs of the Freshwater Algae, 1995).
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P. aenigmaticus
24 x 9 μm
Omiya
Saitama, 2001
P. aenigmaticus
20 x 9 μm
Akigase Park
Saitama, 2002
P. aenigmaticus
20 x 9 μm
Akigase Park
Saitama, 2002
P. aenigmaticus
μm
Hanyu
Saitama, 2003
P. aenigmaticus
26 x 14 μm
Sannoh Park
Saitama
Saitama, 2005
P. aenigmaticus
24 x 11 μm
Okubo Ryoke
Akigase park
Saitama, 2005
P. aenigmaticus ?
or similar sp. ?
30 x 12 μm
Shiba river
near Owada p.
Saitama, 2005
P. aenigmaticus ?
or similar sp. ?
30 x 12 μm
Oura central p.
Oura
Gunma, 2006
P. aenigmaticus ?
20 x 7 μm
A. flower p.
Ashikaga
Tochigi, 2006
P. aenigmaticus ?
20 x 9 μm
Okahotto-Yatsu 4
Abiko
Chiba, 2008
P. aenigmaticus ?
26 x 9 μm
Beppu-numa
Kumagaya
Saitama, 2008