Cerithiopsis albovittata (C.B. Adams, 1850)
Joculator albulus (K.H.J. Thiele, 1930)
Cerithiopsidella alcima (P. Bartsch, 1911)
Seila alfredensis (P. Bartsch, 1915)
Horologica alligata A. Cecalupo & I. Perugia,2012
Joculator alligatus A. Cecalupo & I. Perugia,2012
Horologica alternata A. Cecalupo & I. Perugia,2012
Clathropsis alternata (C.F. Laseron, 1951)
Cerithiopsis althea W.H. Dall, 1927
Notoseila altissima (A.N. Golikov& V.V. Gulbin, 1978)
Cerithiopsis alveolata (FOSSIL) G.P. Deshayes, 1864 †
Cerithiopsis amabilis (C.É. Bayle, 1880)
Synthopsis ambigua A. Cecalupo & I. Perugia,2013
Prolixodens amethysta A. Cecalupo & I. Perugia,2013
Horologica amoena A. Cecalupo & I. Perugia,2013
Synthopsis ampulla A. Cecalupo & I. Perugia,2012
Paraseila ampulla C.F. Laseron, 1956
Cerithiopsis anaitis P. Bartsch, 1918
Marshallopsis anceps A. Cecalupo & I. Perugia,2013
Joculator anconae Cecalupo & Perugia, 2017
Socienna angasi (C.G. Semper, 1874)
Seila angolensis E. Rolán & F. Fernandes,1990
Dizoniopsis angustissima (E. Forbes, 1843)
Joculator angustus Cecalupo & Perugia, 2017
Horologica anisocorda M. Jay & J. Drivas, 2002
Cerithiopsis annae A. Cecalupo & G. Buzzurro,2005
Ondulopsis annae A. Cecalupo & I. Perugia,2012
Horologica annagregis A. Cecalupo & I. Perugia,2013
Cerithiopsidella antefilosa (P. Bartsch, 1911)
Cerithiopsis antemunda P. Bartsch, 1911
Joculator antonioi A. Cecalupo & I. Perugia,2012
Joculator aoreensis A. Cecalupo & I. Perugia,2013
Dizoniopsis apexclarus E. Rolán, 2007
Cerithiopsis apexcostata E. Rolán, J. Espinosa& R. Fernández-Garcés, 2007
Clathropsis apexlevis Cecalupo & Perugia, 2017