Unio mamillatus (FOSSIL) Hislop, 1859 †
Unio mancus J.B.P.A. Lamarck, 1819
Unio mancus hamyanus J.R. Bourguignat, 1885
Unio mancus ilqui Soleillet, 1885
Parreysia mandelayensis W. Theobald, 1873
Lamprotula mansuyi (P. Dautzenberg& H. Fischer, 1908)
Pseudodon manueli Konopleva, Kondakov& Vikhrev, 2017
Lamellidens marginalis (J.B.P.A. Lamarck, 1819)
Alasmidonta marginata T. Say, 1818
Pleurobema marshalli L.S. Frierson, 1927
Elliptio marsupiobesa S.L.H. Fuller, 1972
Psoronaias martensi L.S. Frierson, 1927
Fusconaia masoni (T.A. Conrad, 1834)
Alasmidens mccordi (E.W. Athearn, 1964)
Toxolasma mearnsi C.T. Simpson, 1900
Actinonaias medellina (I. Lea, 1838)
Nephronaias mellea (I. Lea, 1859)
Unio menkei (FOSSIL) F.C.L. Koch & R.W. Dunker,1847 †
Protunio messageri (A.R.J.B. Bavay& P. Dautzenberg, 1901)
Popenaias metallica (T. Say, 1831)
Theliderma metanevra (C.S. Rafinesque, 1820)
Epioblasma metastriata T.A. Conrad, 1838
Potamilus metnecktayi R.I. Johnson, 1998
Sphenonaias mexicana (R.A. Philippi, 1847)
Oxynaia micheloti (L.J. Morlet, 1886)
Oxynaia micheloti hedeius (J.F. Mabille, 1889)
Sphenonaias microdon (E.C. Von Martens, 1887)
Physunio micropteroides T.N. Annandale, 1918
Physunio micropterus (P.M.A. Morelet, 1866)
Lamprotula microsticta (P.M. Heude, 1877)
Pseudanodonta middendorffi (Siemaschko, 1848)
Fusconaia mitchelli (W.H. Dall, 1896)
Actinonaias moctezumensis (H.A. Pilsbry, 1910)
Physunio modelli R.A.M. Brandt, 1974
Pressidens moellendorffi F. Haas, 1910