Buccinum oedematum W.H. Dall, 1907
Pollia ogormani (FOSSIL) (A.E.M. Cossmann, 1923 †)
Clinopegma okhotensis (W.H. Dall, 1925)
Plicifusus okhotskanus (R. Tiba, 1973)
Cominella okinavensis (FOSSIL) F.S. MacNeil, 1960 †
Cantharus okinawa (FOSSIL) F.S. MacNeil, 1960 †
Falsimohnia okutanii (H. Numanami, 1996)
Colus olavi (FOSSIL) (O.A.L. Mörch, 1871 †)
Parvisipho oligocaenica (FOSSIL) R. Marquet, Lenaerts& Laporte, 2016 †
Plicifusus olivaceus (C.W.S. Aurivillius,1885)
Cominella olsoni (R.K. Dell, 1956)
Cantharus olssoni (FOSSIL) E.J. Petuch, 1994 †
Metula olssoni W.P. Woodring, 1928
Aulacofusus ombronius (W.H. Dall, 1919)
Neptunea oncodes (W.H. Dall, 1907)
Penion oncodes (FOSSIL) (R.A. Philippi, 1887 †)
Austrofusus oneroaensis (FOSSIL) Powell & J.A. Bartrum,1929 †
Trominina onnaica (FOSSIL) (Yokoyama, 1932 †)
Cominella onokeana (FOSSIL) (L. C. King, 1933 †)
Pseudoliomesus ooides (A.T. von Middendorff,1848)
Neptunea oomurai (FOSSIL) Y. Otuka, 1940 †
Euthria oostinghi (FOSSIL) C.O. Van Regteren Altena,1950 †
Buccinum opisoplectum W.H. Dall, 1907
Metula optima A.A. Olsson & F.M. Bayer,1972
Aeneator orbitus (FOSSIL) (F.W. Hutton, 1885 †)
Pseudofax ordinarius (FOSSIL) (Marshall, 1917 †)
Bruclarkia oregonensis (FOSSIL) (T.A. Conrad †)
Sulcosinus orientalis A.N. Golikov & V.V. Gulbin,1977
Penion ormesi (A.W.B. Powell, 1927)
Buccinum osagawai T. Habe & K. Itô, 1968
Aeneator otagoensis H.J. Finlay, 1930
Aeneator otagoensis cookiana R.K. Dell, 1956
Euthrenopsis otagoensis A.W.B. Powell, 1929
Cominella otagoensis (H.J. Finlay, 1926)
Cominella otakavica A.W.B. Powell, 1946