Imperium naturæ C. Linnaeus, 1758 - nature
   Mundus Plinius - physical world
     naturalia - natural bodies
       Regnum Animale C. Linnaeus, 1758 - animal kingdom see Kingdom Animalia Linnaeus, 1758
         Class Amphibia Linnaeus, 1758 - amphibians see Class Amphibia Gray, 1825
           Order Nantes Linnaeus, 1758
             Genus Petromyzon Linnaeus, 1758
               1 Petromyzon marinus Linnaeus, 1758 - eel sucker
               2 Petromyzon fluviatilis Linnaeus, 1758 see Lampetra fluviatilis (Linnaeus, 1758)
               3 Petromyzon branchialis Linnaeus, 1758 see Lampetra fluviatilis (Linnaeus, 1758)