[Kingdom] Animalia Linnaeus, 1758 - animals
   Grade Enterozoa
     Grade Cœlomata
       Phylum Mollusca Linnaeus, 1758 - molluscs
         Branch Lipocephala
           Class Tentaculibranchia
             Branch Holobranchia
               Grade Ectoprocta
                 Order Gymnolæma Allman, 1856
                   Genus Flustra Linnaeus, 1767