Lirophora mariae (A.V.M.D. D'Orbigny,1846)
Timoclea marica (C. Linnaeus, 1758)
Tawera marionae H.J. Finlay, 1928
Tawera marshalli (FOSSIL) J. Marwick, 1927 †
Tawera marthae (FOSSIL) J. Marwick, 1928 †
Cyclorismina marwicki (FOSSIL) Zinsmeister, 1984 †
Macrocallista marylandica (FOSSIL) (T.A. Conrad, 1833 †)
Dosinia mastrichtiensis (FOSSIL) E.F. de Vogel, 1895 †
Proxichione materna T. Iredale, 1929
Amiantis mathewsoni (FOSSIL) (W.M. Gabb, 1866 †)
Pitar matsumotoi (FOSSIL) (T. Nagao, 1928 †)
Dosina mauryae (FOSSIL) E.H. Vokes, 1938 †
Tawera mawsoni (C. Hedley, 1916)
Chione mazyckii W.H. Dall, 1902
Callista mcgrathiana (FOSSIL) Rathburn, 1875 †
Pitar medipictus K.L. Lamprell& R.N. Kilburn, 1999
Pitar mediterraneus (A. Aradas & L. Benoit,1872)
Macrocallista meganosensis (FOSSIL) Clark & Woodford, 1927 †
Venus mekranica (FOSSIL) E.W. Vredenburg, 1928 †
Macridiscus melanaegis (A. Römer, 1861)
Lioconcha melharteae K.L. Lamprell & J. Stanisic,1996
Lamelliconcha mellisa (FOSSIL) A.A. Olsson, 1942 †
Dorisca melvilli (H. Lynge, 1909)
Gafrarium menkei (I.H. Jonas, 1846)
Sunetta menstrualis (K.T. Menke, 1843)
Mercenaria mercenaria (C. Linnaeus, 1758)
Mercenaria mercenaria notata T. Say, 1822
Mercimonia mercenaroides (FOSSIL) †
Meretrix meretrix (C. Linnaeus, 1758)
Leukoma meridonalis (FOSSIL) (Sowerby, 1846 †)
Dosinia meridonalis (FOSSIL) H.F.A. von Ihering,1897 †
Sunetta meroe (C. Linnaeus, 1758)
Leukoma metodon (H.A. Pilsbry & H.N. Lowe,1932)
Leukoma metodon mcgintyi (A.A. Olsson, 1961)
Agriopoma mexicanum (L.G. Hertlein& A.M. Strong, 1948)