Clinocardium okushirense (FOSSIL) S. Uozumi & Fujie, 1966 †
Hedecardium olssoni (FOSSIL) J. Marwick, 1944 †
Clinocardium omagariense (FOSSIL) Honda 1981 †
Pseudocatillus omnivagus (FOSSIL) Ebersin, 1967 †
Maoricardium oneroaense (FOSSIL) (Powell, 1938 †)
Onestia onestae (FOSSIL) (McLearn, 1931 †)
Vasticardium orbita (L.A. Reeve, 1845)
Lunulicardia orlini H.K. Mienis, 2009
Keenocardium ornatocostatum (FOSSIL) (Volobueva, 1981 †)
Vasticardium otukai (FOSSIL) K.M. Hatai & S. Nisiyama,1952 †
Cardium ouralicum (FOSSIL) Murchison & al., 1845 †
Acrosterigma oxygonum (G.B. II Sowerby, 1834)
Microcardium panamense (W.H. Dall, 1908)
Cardium pantecolpatum (FOSSIL) A.E.M. Cossmann & M.A. Peyrot †,
Papillicardium papillosum (G.S. Poli, 1791)
Papillicardium papillosum auri (E. Fischer-Piette, 1977)
Vasticardium papuanum E. Vidal, 1996
Protocardia parahillana (FOSSIL) B. Wade, 1926 †
Didacna parallella V.V. Bogachev, 1932
Nemocardium parile (FOSSIL) (G.P. Deshayes, 1858 †)
Trachycardium parile (FOSSIL) W.H. Dall, 1900 †
Discors parisiense (FOSSIL) (A.V.M.D. D'Orbigny,1850 †)
Dinocardium parkinsoni (FOSSIL) (J. de C. Sowerby,1814 †)
Iheringicardium patagonicum (FOSSIL) (H.F.A. von Ihering,1907 †)
Loxocardium patruelinum (FOSSIL) (G.P. Deshayes, 1858 †)
Pseudocatillus patruliusi (FOSSIL) (Papaianopol, 1992 †)
Nemocardium patulum (FOSSIL) (F.W. Hutton 1873 †)
Cerastoderma patuxentium (FOSSIL) L.C. Glenn, 1904 †
Acanthocardia paucicostata (G.B. II Sowerby, 1834)
Acrosterigma paulayi (FOSSIL) E. Vidal, 1999 †
Cardium pauperculum (FOSSIL) M. Yokoyama, 1923 †
Microcardium pazianum (W.H. Dall, 1916)
Vasticardium pectiniforme (I. von Born, 1780)
Cardium pelouatense (FOSSIL) A.E.M. Cossmann& M.A. Peyrot, 1911 †
Microcardium peramabile (W.H. Dall, 1881)