Spissatella lyellii (FOSSIL) (Sowerby, 1846 †)
Crassinella maldonadoensis H.A. Pilsbry, 1897
Hybolophus maleficae (FOSSIL) DeVries, 2016 †
Crassatella manifesta (FOSSIL) Berezovsky, 2010 †
Crassatella maroimensis (FOSSIL) White, 1887 †
Crassinella marplatensis Z.J.A. De Castellanos,1970
Eucrassatella marshalli (FOSSIL) A.W.B. Powell, 1931 †
Crassinella martinicensis (A.V.M.D. D'Orbigny,1853)
Marvacrassatella marylandica (FOSSIL) (T.A. Conrad, 1832 †)
Eucrassatella maudensis (FOSSIL) (G.B. Pritchard, 1903 †)
Spissatella maxwelli (FOSSIL) K.S. Collins, D.M. Crampton& G. Hannah, 2014 †
Spissatella media (FOSSIL) J. Marwick, 1926 †
Hybolophus mediamaricanus (FOSSIL) (J. Brown & H.A. Pilsbry,1913 †)
Eucrassatella mediamericana (FOSSIL) (J. Brown & H.A. Pilsbry,1913 †)
Crassatella meganosensis (FOSSIL) Clark & Woodford, 1927 †
Marvacrassatella melina (FOSSIL) (T.A. Conrad, 1832 †)
Crassatella meridionalis (FOSSIL) W.C. Mansfield, 1929 †
Crassatella merriami (FOSSIL) C.S. Weaver, 1916 †
Salaputium micrum (J.C. Verco, 1895)
Crassinella midiensis (FOSSIL) A.A. Olsson, 1922 †
Anthonya mifunensis (FOSSIL) Tamura, 1977 †
Crassinella minor (FOSSIL) †
Crassatella mississippiensis (FOSSIL) T.A. Conrad, 1848 †
Crassatina modesta (C.B. Adams, 1869)
Salaputium modestum (H. Adams, 1869)
Nipponocrassatella nana (A. Adams & L.A. Reeve,1850)
Indocrassatella natalensis (K.H. Barnard, 1964)
Eucrassatella navigatum (S.L. Lovén, 1846)
Fluctiger navigatus (C. Hedley, 1906)
Hybolophus nelsoni (FOSSIL) (Grzybowski, 1899 †)
Crassatella neorhynchus (FOSSIL) A.A. Olsson, 1931 †
Crassatella neusensis (FOSSIL) L.W. Stephenson, 1923 †
Eucrassatella nipponensis (FOSSIL) M. Yokoyama, 1928 †
Crassinella nuculiformis S.S. Berry, 1940
Eucrassatella oblonga (FOSSIL) (J.E. Tenison-Woods,1876 †)