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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Similar species -- >> P. pleuronectes;
P. triqueter
80 x 50 μm
Uruguay, 1999
P. triqueter
80 x 48 μm
Omachi natural p.
Chiba, 2001
P. triqueter
80 x 55 μm
Uruguay, 1999
P. triqueter
80 x 48 μm
Nanbata castle p.
Fujimi
Saitama, 2005
P. triqueter
75 x 45 μm
Izumo Shrine
Izumo
Shimane, 2006
P. triqueter
74 x 45 μm
Uruguay, 1999
P. triqueter ?
μm
Michi-no-eki
Tsukiyono
Gunma, 2003
P. triqueter
70 x 47 μm
near Town Hall
Shobu
Saitama, 2004
P. triqueter
65 x 40 μm
Fujimi
Saitama, 2003
P. triqueter
60 x μm
Iruma
Saitama, 2003
P. triqueter
57 x 40 μm
Mizuko-kaizuka p.
Fujimi
Saitama, 2003
P. triqueter
56 x μm
chl. 2-3 μm
Kodama
Saitama, 2003
P. triqueter
55 x 40 μm
Mizuko-kaizuka p.
Fujimi
Saitama, 2004
P. triqueter
48 x 36 μm
Ichikawa
Chiba, 2001
P. triqueter
47 x 35 μm
Aizu Recreation p.
Aizuwakamatsu
Fukushima, 2005
P. triqueter
44 x 37 μm
Higashi-Urawa
Saitama, 2001
P. triqueter
μm
near Nan-ko
Shirakawa
Fukushima, 2003
P. triqueter ?
43 x 30.5 μm
Mihashi Park
Saitama, 2002
P. triqueter ?
40 x 22 μm
Watarase Wetland
Fujioka
Tochigi, 2005
P. triqueter ?
40 x 30 μm
Kareki-numa
Nikko
Tochigi, 2008
P. triqueter
35 x μm
Shimotsuma
Ibaraki, 2003