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 Notaspidea Fischer, 1883 [monotypic] see Suborder Notaspidea Fischer, 1883
         Superfamily Pleurobranchoidea Gray, 1827
           Family Tylodinidae Gray, 1847
             1 Genus Tylodina Rafinesque, 1814
             2 Genus Roya Iredale, 1912