[Kingdom] Animalia Linnaeus, 1758 - animals
   Grade Enterozoa
     Grade Cœlentera
       Phylum Nematophora Huxley, 1850
         Class Hydromedusæ see Class Hydrozoa Owen, 1843
           Order Siphonophora Eschscholtz, 1829 - siphonophorans
             1 Genus Physophora Péron & Lesueur, 1807
             2 Genus Velella Lamarck, 1801