Spisula precursor (FOSSIL) W.H. Dall, 1909 †
Mactra proaspera F. Sacco, 1900
Oxyperas proaspersa (FOSSIL) (F. Sacco, 1901 †)
Mactra procrassa (FOSSIL) Woods, 1850 †
Mactra protoreevesii (FOSSIL) Noetling, 1901 †
Mactra pulchella R.A. Philippi, 1846
Raeta pulchella (A. Adams & L.A. Reeve,1850)
Mactra pura L.A. Reeve, 1854
Mactra pusilla R.A. Philippi, 1887
Anatina putatoria (FOSSIL) White, 1887 †
Willimactra putida (FOSSIL) Saul, 1973 †
Mactra pyrenaicensis (FOSSIL) A.E.M. Cossmann, 1923 †
Mactra quadrangularis L.A. Reeve, 1854
Mactra quadrangularis veneriformis G.P. Deshayes in L.A. Reeve,1854
Mactra queenslandica Smith, 1914
Mactra quirosana F. Hodson, 1931
Mactromeris ramonensis (FOSSIL) A. Packard & Clark,1915 †
Spisula rappahannockensis (FOSSIL) Gardner, 1944 †
Spisula raveneli (T.A. Conrad, 1832)
Austromactra recondita (FOSSIL) (G.P. Deshayes, 1857 †)
Mactrinula reevesii (J.E. Gray, 1837)
Lutraria rhynchaena I.H. Jonas, 1844
Tanysiphon rivalis W.H. Benson, 1858
Mactra rochebrunei É. Lamy, 1916
Barymactra rostrata (L. Spengler, 1802)
Austromactra rufescens (J.B.P.A. Lamarck, 1818)
Eastonia rugosa (FOSSIL) (G.S. Helbling, 1779 †)
Mactromeris rushi (FOSSIL) Wagner & Schilling,1923 †
Darina rustica M. Huber, 2010
Spisula sachalinensis (L. von Schrenck, 1862)
Trinitasia sanctiandreae (FOSSIL) (C.J. Maury, 1925 †)
Lutraria sanna (FOSSIL) B. de Basterot, 1825 †
Mulinia sapotilla (FOSSIL) W.H. Dall, 1898 †
Mactra sauliana J.E. Gray, 1838
Lutraria scaldensis (FOSSIL) Urk, 1980 †