Kingdom [Animalia] Linnaeus, 1758 - animals
   Subkingdom Protozoa Goldfuss, 1818 see Kingdom Protozoa Goldfuss, 1818
     Class Ciliata see [unranked] ciliates
       Order Spirotricha
         Suborder Heterotricha Stein, 1859
           1 Genus Stentor Oken, 1815
           2 Genus [Spirostomum] Ehrenberg, 1834
           3 Genus [Nyctotherus] Leidy, 1849
           4 Genus [Bursaria] Müller, 1773
           5 Genus [Balantidium] Claparède & Lachmann, 1858