Alaginella ochracea (G.F. Angas, 1871)
Bullata odoricyi (M. Bernardi, 1852)
Eratoidea oettlyi J. Espinosa & J.A. Ortea,2013
Prunum olivaeforme (L.C. Kiener, 1834)
Marginella olivarum S.G. Veldsman& J.H. Veldsman, 2015
Mesoginella olivella (L.A. Reeve, 1865)
Glabella omanensis F. Boyer, 2014
Prunum onchidella (FOSSIL) (W.H. Dall, 1890 †)
Volvarina ondina J. Espinosa, L. Moro& J.A. Ortea, 2011
Granulina oneili J. Espinosa & J.A. Ortea,2014
Microspira onichidella (FOSSIL) W.H. Dall, 1890 †
Granulina opima (C.F. Laseron, 1957)
Protoginella opoitia (FOSSIL) (J. Marwick, 1965 †)
Serrata orientalis F. Boyer, 2008
Marginella ornata J.H. Redfield, 1870
Volvarina orozcoae J.A. Ortea, 2014
Marginella orstomi H.E. Coomans, 1975
Volvarina oryzoides (FOSSIL) J. Gardner, 1937 †
Hyalina oscaritoi J. Espinosa, L. Moro& J.A. Ortea, 2011
Volvarina osmani J. Espinosa, J.A. Ortea& L. Moro, 2008
Dentimargo osmayi J. Espinosa & J.A. Ortea,2014
Hydroginella osteri (F.P. Jousseaume, 1875)
Mesoginella otagoensis (R.K. Dell, 1956)
Volvarina oteroi J. Espinosa, J.A. Ortea& G. Pérez-Dionis, 2014
Granulina ovata T. McCleery, 2010
Serrata ovata F. Boyer, 2008
Prunum oviformis (FOSSIL) (T.A. Conrad, 1868 †)
Cryptospira ovulata (FOSSIL) (J.B.P.A. Lamarck,1803 †)
Granulina ovuliformis (A.V.M.D. D'Orbigny,1842)
Ovaginella ovulum (G.B. II Sowerby, 1846)
Triginella pachia (R.B. Watson, 1886)
Marginella pachista J.R. le B. Tomlin, 1913
Prunum pacotalaverai J. Espinosa, J.A. Ortea& L. Moro, 2014
Alaginella palla (B.C. Cotton, 1949)
Volvarina pallasae J. Espinosa & J.A. Ortea,2015