Genus: Cigar- or foot-shaped; a single macronucleus and 1 to several vesicular or compact microuclei (Kudo, 1966).
Species: 180-300 μm long; a compact micronucleus; two contractile vacuoles (Kudo, 1966). Cylindrical or cigar-shaped; rounded anteriorly, pointed posteriorly; one large compact micronucleus ("caudatum" group) approximately 8 μm diam.; two contractile vacuoles; 170-290 μm long (Wichterman, 1986). Elongate, rounded anteriorly, pointed posteriorly; caudal cilia present; 180-280 μm long; a single macronucleus with a single micronucleus; two contractile vacuoles (Carey, 1992).

Organelles and Endosymbionts
P. caudatum mac. & mic. 240 x 95 μm by Y. Tsukii	P. caudatum CV pores mac. & mic. Kazo Saitama, 2003	P. caudatum nucleolus by Y. Tsukii	P. caudatum trichocysts, cilia & mitochondria? by Y. Tsukii
P. caudatum 250 x 62 μm mac. endosymbionts near Kondo-numa Tatebayashi Gunma, 2006
Vegetative cells
P. caudatum 290 x 73 μm Nishi-Urawa Saitama, 2003	P. caudatum 260 x 85 μm drainage ditch Kurihashi Saitama, 2006	P. caudatum 250 x 72 μm Gyoda general p. Gyoda Saitama, 2006	P. caudatum 241 x 60 μm 217 x 55 μm by Y. Tsukii
P. caudatum 220 x 57 μm by H. Horikami	P. caudatum 207 x 54 μm by Y. Tsukii	P. caudatum body flattened 260 x 98 μm by A. Yanagi	P. caudatum μm by K. Mikami
P. caudatum 220 x 70 μm Furu-tone river Kasukabe Saitama, 2004	P. caudatum 218 x 63 μm Demaru-nakago Kawajima Saitama, 2005	P. caudatum 205 x 57 μm Kitamoto nature o.p. Kitamoto Saitama, 2005	P. caudatum 200 x 65 μm Oura central p. Oura Gunma, 2006
P. caudatum 225 x 63 μm Kami-omino Kawajima Saitama, 2006	P. caudatum 180 x 40 μm Hazama marsh Ashikaga Tochigi, 2006	P. caudatum 222 x 51 μm Azami-ike 1 Norikura highland Nagano, 2007	P. caudatum 260 x 120 μm Yaita-machi Utsunomiya Tochigi, 2006
P. caudatum 195 x 45 μm Takao-sakura p. Kitamoto Saitama, 2005	P. caudatum or P. multi. ? 215 x 45 μm Akebono marsh Tsuchiyu-onsen Fukushima, 2005	P. caudatum or P. multi. ? 220 x 60 μm near Otto-Numa Tsuchiura Ibaraki, 2006	P. caudatum or P. multi. ? 250 x 62 μm drainage ditch Kawagoe Saitama, 2006

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