Kingdom Protista (Haeckel, 1866) - protists Phylum Ciliophora Doflein, 1901 - ciliates Class Polyhymenophorea - spirotrichs see Class Spirotrichea Bütschli, 1889 Subclass Spirotricha see Class Spirotrichea Bütschli, 1889 Order Hypotrichida Stein, 1859 - hypotrichs see Subclass Hypotrichia (Stein, 1859) Cavalier-Smith, 1993 Genus Hypotrichidium Ilowaisky, 1921