Margarella achilles (H. Strebel, 1908)
Tristichotrochus aculeatus (G.B. III Sowerby, 1912)
Tristichotrochus aculeatus aliguayensis G.T. Poppe, S.P. Tagaro& H. Dekker, 2006
Maurea acutangula (FOSSIL) (H.H. Suter, 1917 †)
Calliostoma adelae J.S. Schwengel, 1951
Calliostoma admirandum E.A. Smith, 1906
Calliostoma adspersum (R.A. Philippi, 1851)
Calliostoma aequisculptum P.P. Carpenter, 1865
Calliostoma africanum P. Bartsch, 1915
Calliostoma aikeni M. Lussi, 2014
Calliostoma akoya J.T. Kuroda in N. Ikebe,1942
Calliostoma alboregium M. Azuma, 1961
Alertalex alertae (B.A. Marshall, 1995)
Calliostoma alisi B.A. Marshall, 1995
Coralastele allanae (T. Iredale, 1930)
Calliostoma allporti (J.E. Tenison-Woods,1876)
Calliostoma altena J. Knudsen, 1970
Calliostoma alternum J.F. Quinn, 1992
Calliostoma aluminium W.H. Dall, 1892
Calliostoma anderssoni H. Strebel, 1908
Calliostoma angolense F. Boyer, 2006
Calliostoma annulatum (J. Lightfoot, 1786)
Astele anonima (FOSSIL) (Fabiana, 1915 †)
Calliostoma anseeuwi G.T. Poppe, S.P. Tagaro& H. Dekker, 2006
Margarella antarctica (É. Lamy, 1905)
Calliostoma antipodense (B.A. Marshall, 1995)
Calliostoma antonii (F.C.L. Kochin R.A. Philippi, 1843)
Calliostoma aphelium (FOSSIL) W.H. Dall, 1892 †
Calliostoma apicinum W.H. Dall, 1881
Calliostoma aporia C. Vilvens, 2009
Calliostoma aprosceptum C. Vilvens, 2009
Fautrix aquilonia B.A. Marshall, 1995
Calliostoma argentum J.F. Quinn, 1992
Astele armillata (W. Wood, 1828)
Calliostoma arx C. Vilvens, 2005