Architectonica acuta (FOSSIL) T.A. Conrad, 1854 †
Discotectonica acuta (FOSSIL) (J.E. Tenison-Woods,1879 †)
Solatisonax acutecarinata (K.H.J. Thiele, 1925)
Discotectonica acutissima (G.B. III Sowerby, 1914)
Juliania aequistriata (FOSSIL) (H.F.A. von Ihering,1907 †)
Juliania aequistriata casamajorensis (FOSSIL) Morra & Del Rio, 1987 †
Architectonica aethiops K.T. Menke, 1830
Architectonica affinis (FOSSIL) Sowerby, 1840 †
Dinaxis alabamense (FOSSIL) (W.H. Dall, 1892 †)
Discotectonica alfi Thach, 2017
Solatisonax alleryi (G. Seguenza, 1876)
Nipteraxis alonzensis (FOSSIL) J.M. Pacaud, 2017 †
Pseudotorinia aloysii (R. Selli, 1973)
Stellaxis alveatum (FOSSIL) (T.A. Conrad, 1833 †)
Architectonica ammonites (FOSSIL) J.B.P.A. Lamarck, 1804 †
Architectonica amoena (FOSSIL) T.A. Conrad, 1854 †
Pseudotorinia amoena (R. Murdoch & H.H. Suter,1906)
Rinaldoconchus ampezzanus (FOSSIL) Zardini, 1980 †
Solarium amphitermum (FOSSIL) W.H. Dall, 1892 †
Astronacus anaglyptus (FOSSIL) W.P. Woodring, 1959 †
Architectonica angsanana (FOSSIL) (K. Martin, 1922 †)
Architectonica angustiforatum (FOSSIL) (A.E.M. Cossmann& M.A. Peyrot, 1921 †)
Disculus antoinei P.M. Pallary, 1936
Architectonica arcana R. Bieler, 1993
Pseudotorinia architae (O.G. Costa, 1841)
Pseudotorinia architae cristallina (G.W. Nowell-Usticke,1969)
Pseudotorinia architae retifera (W.H. Dall, 1892)
Heliacus areola (J.F. Gmelin, 1791)
Heliacus areola bicanaliculatus (A. Valenciennes, 1832)
Spirolaxis argonauta R. Bieler, 1993
Architectonica ariei (FOSSIL) Wienrich & Janssen,2007 †
Pseudotorinia armillata R. Bieler, 1993
Architectonica arthuri (FOSSIL) Vasseur, 1881 †
Pseudomalaxis asculpturatus (FOSSIL) P.A. Maxwell, 1966 †
Granosolarium asperum (R.B. Hinds, 1844)