Family: Unicells; planktonic; cell body spherical, ellipsoidal, ovoid, fusiform or polygonal in shape; cell wall smooth in most species; chloroplasts without pyrenoids; leucosin granules present (Illustrations of The Japanese Fresh-water Algae, 1977).
Genus: Unicells, planktonic; cell body guadrangular, each corner drawn out and branched two times forming 2-3 short, thick projections; many chloroplasts disc-shaped, without pyrenoids (Guide book to the "Photomicrographs of the Freshwater Algae", 1998).

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P. hastatum cell 43 μm Mizumoto park Tokyo, 2001	P. hastatum 32 x 34 μm Kondo-numa p. Tatebayashi Gunma, 2007
P. lobulatum x 43 μm Dedono-yu Nishiwaga Iwate, 2007	P. lobulatum cell μm O-ike park Yabuki Fukushima, 2003	P. lobulatum cell x 37 μm water reservoir near Yamaguchi Univ. Yamaguchi, 2004	P. lobulatum ? cell 38 μm Sayama Natural Park Tokyo, 2001
Pseudostaurastrum sp. cell 33 μm Kawashima or Kawajima Saitama, 2002	P. lobulatum cell 47 μm Shikinawa-ike Fukuoka, 2001

Similar genus -->> Staurastrum; Tetraedron;

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