Phylum Mollusca Linnaeus, 1758 - molluscs
   Class Bivalvia Linnaeus, 1758 - bivalves
     Subclass Heterodonta Neumayr, 1884 see Clade Heterodonta Neumayr, 1884
       Order Chamida see Order Venerida Gray, 1854
         Superfamily Veneroidea Rafinesque, 1815
           Family Veneridae Rafinesque, 1815 - venus clams
             Subfamily Chioninae Frizzell, 1936, nom. illeg.
               Genus Protothaca Dall, 1902
                 Subgenus Callithaca Dall, 1902