Nemocardium khomenkoi (FOSSIL) A.I. Kafanov& K. Ogasawara, 1999 † Russia, Sakhalin
Cardium khowaiteri (FOSSIL) Abbass, 1972 † Saudi Arabia, Ash Sharqiyah
Trachycardium kinsmarae (FOSSIL) J. Makiyama, 1934 † Russia, Sakhalin
Frigidocardium kiranum K. Sakurai & T. Habe,1966 Réunion12 mm
Ciliatocardium kirkerensis (FOSSIL) (Clark, 1918 †)
Laevicardium kirkinskayae (FOSSIL) Krishtofovich, 1957 † Russia, Sakhalin
Fragum kishimaense (FOSSIL) (Nagao) †
Keenocardium kljutschiense (FOSSIL) (Krishtofovich, 1969 †) Eastern Kamchatka
Monodacna knipowitschi (B.M. Logvinenko& Y.I. Starobogatov, 1966) Caspian Sea
Parvicardium kochi (FOSSIL) (C.G. Semper, 1861 †) Germany, Mecklenburg9 mm
Protocardia koshikijimensis (FOSSIL) K. Amano, 1958 † Japan, Amakusa-Shimoshima
Laevicardium kovacovense (FOSSIL) Senes, 1958 † Hungary, Bükk28 mm
Nemocardium kovatschensis (FOSSIL) L. Krishtofovich, 1947 † Western Kamchatka
Vasticardium kuboderai N.N. Thach, 2015 Vietnam86,4 mm
Keenocardium kuluvense (FOSSIL) A.I. Kafanov, 1984 † Western Kamchatka
Laevicardium kuluvense (FOSSIL) V.N. Sinelnikova, 1980 † Western Kamchatka
Granocardium kummeli (FOSSIL) (Weller, 1907 †) Tennessee31 mm
Cardium kunstleri (FOSSIL) A.E.M. Cossmann& M.A. Peyrot, 1911 † Portugal, Algarve150 mm
Fulvia kurodai (FOSSIL) K.M. Hatai& S. Nisiyama, 1958 † Japan, Tokyo
Trachycardium lacunosum (FOSSIL) (L.A. Reeve, 1845 †) Egypt, Red Sea62 mm
Fulvia laevigata (C. Linnaeus, 1758) Bahamas24 mm
Fulvia laevigata papyracea (J.G. Bruguière, 1789) South Africa, Durban32,6 mm
Adacna laeviuscula (K.E.I. von Eichwald,1829) Caspian Sea
Serripes laperousii (G.P. Deshayes, 1839) Japan, Wakkanai
Chesacardium laqueatum (FOSSIL) (T.A. Conrad, 1830 †) USA, Florida, Leon
Papyridea lata (I. von Born, 1778) Bahamas23 mm
Nemocardium lene (FOSSIL) (T.A. Conrad, 1856 †) United States, Alabama, Clarke
Cardium lennieri (FOSSIL) A.E.M. Cossmann& G. Pissarro † France, Normandy5 mm
Cardium leognanense (FOSSIL) C. Mayer, 1866 † France, Aquitaine24 mm
Phlogocardia leonense (FOSSIL) W.C. Mansfield, 1932 † USA, Florida, Leon
Chesacardium leptopleura (FOSSIL) (T.A. Conrad, 1841 †)
Laevicardium leptorinum (FOSSIL) D.T. Dockery, 1982 † USA, Mississippi13 mm
Parvicardium levesquei (FOSSIL) (Orbigny, 1850 †) France, Paris Basin15 mm
Dinocardium levyi (FOSSIL) H.G. Richards, 1953 † Florida36,3 mm
Americardia lightbourni Y.C. Lee & M. Huber, 2012 Bermuda