Protozoa Goldfuss, 1818 - protozoans Phylum Ciliophora Doflein, 1901 - ciliates Class Polyhymenophorea - spirotrichs see Class Spirotrichea Bütschli, 1889 Subclass Spirotrichia Order Hypotrichida Stein, 1859 - hypotrichs see Subclass Hypotrichia (Stein, 1859) Cavalier-Smith, 1993