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
           1.1 Family Umbraculidae Dall, 1889 (1827)
           1.2 Family Tylodinidae Gray, 1847
           2.1 Family Pleurobranchidae Gray, 1827