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: 80-100 μm; similar to P. longicauda; twisted 40-60 degree (How to know the protozoa, 1979).

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Var. torta (= Phacus tortus (Lemmermann) Skvortzow 1928): twisted 40-60 degree
v. torta cell 79 x 56 μm tail 62 μm anterior wide Japan, 1997	v. torta cell 51 x 39 μm tail 27 μm anterior narrowed Japan, 1998	v. torta cell 48 x 39 μm tail 23 μm anterior narrowed Japan, 1999 Movies	v. torta cell 55 x 41 μm tail 35 μm anterior narrowed Uruguay, 1999
v. torta cell 95 x 45 μm tail 43 μm Iyari marsh 1 Omachi Nagano, 2007	v. torta cell μm tail μm Hazama marsh Ashikaga Tochigi, 2003	v. torta cell 63 x 42 μm tail 35 μm anterior narrowed Mihashi Park Saitama, 2002	v. torta cell 85 x 38 μm tail μm Ko-numa Tsukiyono Gunma, 2007
v. torta μm tail μm Lake Biwa Kusatsu Shiga, 2008
Var. tortuosa: twisted about 90 degree (or P. helikoides Pochmann, 1942 ?)
v. tortuosa anterior wide cell 60 x 42 μm tail 25 μm Uruguay, 1999	v. tortuosa anterior wide cell 47 x ? μm tail 25 μm Uruguay, 1999	v. tortuosa cell 50 x 40 μm tail 32 μm Kosugi Toyama, 2002	v. tortuosa anterior wide cell μm tail μm Tsuchiura Ibaraki, 2003
P. torta (tortus) v. tortuosa anterior wide cell μm tail μm Kodama Saitama, 2003	P. torta (tortus) v. tortuosa anterior wide cell μm Yoshimi athletic p. Yoshimi Saitama, 2004
Var. tortuosa (= Phacus helikoides Pochmann 1942): twisted more than 90 degree
v. tortuosa anterior wide cell 100 x 53 μm tail 50 μm Japan, 199?	v. tortuosa anterior narrowed x μm tail μm Saitama, 1999	v. tortuosa anterior narrowed cell x μm tail μm Uruguay, 1999	v. tortuosa 75 x 35 μm Imou bog Toyohashi Aichi, 2004
v. tortuosa anterior narrowed cell x 39 μm tail μm near Town Hall Shobu Saitama, 2004	v. tortuosa cell 68 x 28 μm Higashi-sano Hakuba Nagano, 2004	v. tortuosa or P. sesquitortus ? cell 110 x 44 μm Tane-ike Togakushi highland Nagano, 2005	v. tortuosa 125 x 52 μm Iyari marsh 1 Omachi Nagano, 2007
v. tortuosa μm Tamogi-ike 1 Iiyama Nagano, 2008	v. tortuosa ? 104 x 37 μm 86 x 42 μm Mihashi Park Saitama, 2002	v. tortuosa ? μm μm Kodama Saitama, 2003	v. tortuosa ? 114 x 37 μm Suga-daira m. Ueda Nagano, 2006

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