Phylum Mollusca Linnaeus, 1758 - molluscs
   Class Gastropoda Cuvier, 1795 - snails and slugs
     Subclass Heterobranchia Burmeister, 1837 [monotypic] see Superorder Heterobranchia Burmeister, 1837
       Order Heterostropha Fischer, 1885
         Superfamily Valvatoidea Gray, 1840
           1 Family Valvatidae Gray, 1840
           2 Family Orbitestellidae Iredale, 1917