Phylum [Mollusca] Linnaeus, 1758 - molluscs
   Class Gastropoda Cuvier, 1795 - snails and slugs
     Subclass Prosobranchia Milne-Edwards, 1848 - prosobranchs see Class Gastropoda Cuvier, 1795
       Order Mesogastropoda Thiele, 1925 - mesogastropods see [unranked] mesogastropods
         Suborder Taenioglossa see Order Mesogastropoda Thiele, 1925
           Superfamily Tonnacea Suter, 1913 see Superfamily Tonnoidea Suter, 1913 (1825)
             Family Cassidae P.A. Latreille, 1825 - helmet snails see Subfamily Cassinae Latreille, 1825
               1 Genus Casmaria Adams & Adams, 1853
               2 Genus Cassis Scopoli, 1777
               3 Genus Galeodea Link, 1807
               4 Genus Morum Röding, 1798
               5 Genus Phalium Link, 1807