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 Mactroidea Lamarck, 1809
           Family Mactridae Lamarck, 1809 - surf clams
             Subfamily Mactrinae Lamarck, 1809
               Genus Spisula Gray, 1837
                 1 Subgenus Crassula Marwick, 1948
                 2 Subgenus Hemimactra Swainson, 1840
                 3 Subgenus Notospisula Iredale, 1930
                 4 Subgenus Oxyperas Mörch, 1853
                 5 Subgenus Pseudoxyperas Sacco, 1901
                 6 Subgenus Ruellia Cossmann, 1913
                 7 Subgenus Standella Gray, 1853
                 8 Subgenus Symmorphomactra Dall, 1894