Phylum Mollusca Linnaeus, 1758 - molluscs
   Class Gastropoda Cuvier, 1795 - snails and slugs
     Subclass Opisthobranchia Milne-Edwards, 1848 - opisthobranchs see Order Opisthobranchia Milne-Edwards, 1848
       Order Cephalaspidea Fischer, 1883
         1 Superfamily Acteonoidea d'Orbigny, 1843
         2 Superfamily Bulloidea Gray, 1827
         3 Superfamily Runcinoidea Adams & Adams, 1854