Abbottella abbotti P. Bartsch, 1946
Annularisca aberrans C. de la Torre & P. Bartsch,1941
Chondropoma abnatum (J. Gundlachin L. Pfeiffer, 1858)
Tudora abtiana (L. Pfeiffer, 1862)
Opisthosiphon acklinsensis P. Bartsch, 1946
Parachondria adamsi (L. Pfeiffer)
Abbottella adolphi (L. Pfeiffer, 1858)
Abbottella adolphi peninsularis P. Bartsch, 1946
Abbottella aenea G.T. Watters, 2010
Chondrothyretes affinis C. de la Torre & P. Bartsch,1938
Eutudora agassizi (J.G.F. de Charpentierin L. Pfeiffer, 1852)
Troschelvindex agrestis (L. Pfeiffer, 1862)
Licina aguadillensis (L. Pfeiffer, 1875)
Licina aguadillensis penoensis H.B. Baker, 1940
Wrightudora aguayoi (C. de la Torre& P. Bartsch, 1941)
Xenopoma aguayoi (C. de la Torre& P. Bartsch, 1941)
Bermudezsiphona aguilerianum (R. Arango & Y. Molina,1876)
Annularisca alata (L. Pfeiffer, 1851)
Annularisca alayoi (M.L. Jaume, 1984)
Chondropoma alayoi C.G. Aguayo & M.L. Jaume,1957
Troschelvindex alayoi C.G. Aguayo & M.L. Jaume,1947
Chondropoma alberti W.J. Clench & C.G. Aguayo,1948
Otopoma albicans (J.E. Gray& G.B. I Sowerby, 1839)
Otopoma albicans balfouri (H.H. Godwin-Austen,1881)
Colobostylus albus (G.B. Sowerby, 1843)
Colobostylus albus fuscus (C.B. Adams, 1851)
Chondrothyrium alcaldei M.L. Jaume& Sánchez De Fuentes, 1943
Opisthosiphon alleni P. Bartsch, 1946
Tropidophora alluaudi P. Dautzenberg, 1894
Tropidophora alluaudi pallida P. Dautzenberg, 1894
Tropidophora alluaudi saturata P. Dautzenberg, 1894
Chondropomium alyshae G.T. Watters & G. Duffy,2010
Tropidophora ambilobeensis E. Fischer-Piette, F. Blanc& F. Salvat, 1969
Parachondria anatolensis Watters, 2016
Tropidophora anceps (E.C. Von Martens, 1878)