Chlamys nupera (FOSSIL) T.A. Conrad, 1854 †
Nanaochlamys nutteri (FOSSIL) (R. Arnold, 1906 †)
Cryptopecten nux (L.A. Reeve, 1853)
Pecten oatus (FOSSIL) A.A. Olsson, 1922 †
Hinnites obliquus (FOSSIL) Münster, 1841 †
Dentamussium obliteratum (FOSSIL) (Lamarck) †
Dentamussium obliteratum (C. Linnaeus, 1758)
Korobkovia oblonga (FOSSIL) (R.A. Philippi, 1844 †)
Pecten oblongus (FOSSIL) R.A. Philippi, 1893 †
Giraliapecten oboloides (FOSSIL) Darragh & Kendrick 199 †
Camptochlamys obscurus (FOSSIL) (Sowerby, 1818 †)
Amusium ocalum (FOSSIL) W.H. Dall †
Neithea occidentalis (FOSSIL) (T.A. Conrad, 1855 †)
Pecten ochlockoneensis (FOSSIL) W.C. Mansfield, 1932 †
Maclearnia ochotica (FOSSIL) Milova, 1985 †
Pecten ocklockoneensis (FOSSIL) (W.C. Mansfield, 1932 †)
Yabepecten okiensis (FOSSIL) T. Matsubara, 2014 †
Leptopecten olgensis (FOSSIL) W.C. Mansfield, 1939 †
Towaipecten ongleyi (FOSSIL) (J. Marwick, 1965 †)
Aequipecten opercularis (C. Linnaeus, 1758)
Aequipecten opercularis audouinii (B.C.M. Payraudeau, 1826)
Aequipecten opercularis lineata (E.M. Da Costa, 1778)
Aequipecten opercularis mauritiana (C. Linnaeus, 1758)
Argopecten operculiformis (FOSSIL) F. Toula, 1909 †
Chlamys opuntia (FOSSIL) W.H. Dall, 1898 †
Prohinnites ordonesi (FOSSIL) Imlay, 1940 †
Patinopecten oregonensis (FOSSIL) H.V.W. Howe, 1922 †
Patinopecten oregonensis cancellosus (FOSSIL) (Moore †)
Amusium orientale (FOSSIL) A. Dey, 1961 †
Caribachlamys ornatus (J.B.P.A. Lamarck, 1819)
Lyriochlamys otianus (FOSSIL) (McLearn, 1939 †)
Chlamys otukae (FOSSIL) O. Masuda & Sawada,1961 †
Nanaochlamys otutumiensis (FOSSIL) (S. Nomura & K.M. Hatai,1937 †)
Bractechlamys oweni (A. De Gregorio, 1884)
Leptopecten pabloensis (FOSSIL) (T.A. Conrad, 1857 †)