Crenella abbotti C.O. Van Regteren Altena,1968
Benthomodiolus abyssicola (J. Knudsen, 1970)
Dacrydium abyssorum J.A. Allen, 1998
Promytilus acinaciformis (FOSSIL) Harrington, 1955 †
Admytilus acutangulus (FOSSIL) (G.P. Deshayes, 1830 †)
Mytilus acutirostris (FOSSIL) C.L.F. von Sandberger,1863 †
Crenella adamsiana J.C. Melvill & R. Standen,1907
Brachidontes adamsianus (R.W. Dunker, 1857)
Tumidimytilus addicotti (FOSSIL) A.I. Kafanov, 1985 †
Modiolus adelaidensis (FOSSIL) R. Tate, 1886 †
Gibbomodiola adriatica (J.B.P.A. Lamarck, 1819)
Bathymodiolus aduloides J. Hashimoto & T.A. Okutani,1994
Modiolus aequalis (FOSSIL) J. de C. Sowerby, 1818 †
Lithophaga affinis (FOSSIL) Martin, 1879 †
Mytilus affinis (FOSSIL) Sowerby, 1829 †
Lioberus agglutinans (F.J. Cantraine, 1835)
Musculus aizyensis (FOSSIL) A.E.M. Cossmann, 1886 †
Brachidontes alabamensis (FOSSIL) T.H. Aldrich, 1895 †
Gibbomodiola albicosta (J.B.P.A. Lamarck, 1819)
Dacrydium albidum J.P.L. Pelseneer, 1903
Musculus alganus C.F. Laseron, 1956
Semimytilus algosus (Gould, 1850)
Plicatomytilus allisoni (FOSSIL) A.I. Kafanov, 1985 †
Assytilus alpha (FOSSIL) Berezovsky, 2015 †
Modiolus altijugatus (FOSSIL) J. Marwick, 1931 †
Modiolus ameghinoi (FOSSIL) H.F.A. von Ihering,1907 †
Amygdalum americanum T. Soot-Ryen, 1955
Modiolus americanus (W.E. Leach, 1815)
Modiolus americanus pseudotulipus A.A. Olsson, 1961
Persiaster ancestralis (FOSSIL) Repin, 2008 †
Ciboticola andersoni (E.C. Von Martens, 1887)
Brachidontes andinus (FOSSIL) A.E. Ortmann, 1900 †
Dacrydium angulare K.W. Ockelmann, 1983
Semimodiola angularis (FOSSIL) (G.P. Deshayes, 1830 †)
Modiolus angulatus (FOSSIL) Slodkewitsch, 1981 †