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 Thecosomata Blainville, 1824 [monotypic] - shelled pteropods see Suborder Thecosomata Blainville, 1824
         Suborder Euthecosomata Meisenheimer, 1905 [monotypic] see Infraorder Euthecosomata Meisenheimer, 1905
           Superfamily Spiratelloidea see Superfamily Cavolinioidea Gray, 1850 (1815)
             Family Cavoliniidae Gray, 1850 (1815)
               Subfamily Cavoliniinae Gray, 1850 (1815)
                 Genus Diacria Gray, 1840