[Kingdom] Animalia Linnaeus, 1758 - animals
   Grade Enterozoa
     Grade Cœlomata
       Phylum Mollusca Linnaeus, 1758 - molluscs
         Branch Eucephala
           Grade Echinoglossa
             Class Cephalopoda Cuvier, 1795 - cephalopods
               Grade Pteropoda Cuvier, 1804
                 Order Thecosoma
                   1 Genus Hyalæa Lamarck, 1799
                   2 Genus Criseis Forbes, 1844