[Kingdom] Animalia Linnaeus, 1758 - animals
   Grade Enterozoa
     Grade Cœlentera
       Phylum Nematophora Huxley, 1850
         Class Hydromedusæ see Class Hydrozoa Owen, 1843
           Order Hydriformes
             1 Genus Hydra Linnaeus, 1758
             2 Genus Tubularia Linnaeus, 1758
             3 Genus Sertularia Linnaeus, 1758