Nucula obtusa J.B.P.A. Lamarck, 1799
Nucula obtusa (FOSSIL) Sowerby, 1836 †
Nuculavus okawensis (FOSSIL) (H.G. Schenck, 1939 †)
Ennucula oliva R.N. Kilburn, 1999
Nuculoidea opima (FOSSIL) (J.W. Hall, 1843 †)
Nucula oppressa W. Bergmans, 1991
Nucula orbicella (FOSSIL) A.A. Olsson, 1922 †
Ennucula orekta T. Iredale, 1939
Nuculopsis orientalis (FOSSIL) M. Ichikawa, 1951 †
Leionucula osawanoensis (FOSSIL) (K. Tsuda, 1959 †)
Truncacila osugii (FOSSIL) T. Nagao & Huzioka,1941 †
Ennucula otamaringaensis (FOSSIL) (J. Marwick, 1926 †)
Linucula otamatea (FOSSIL) (C.R. Laws, 1941 †)
Nuculopsis oviformis (FOSSIL) C.O. Waterhouse, 1964 †
Nucula ovula (FOSSIL) Lea, 1833 †
Truncacila oyamadensis (FOSSIL) K. Hirayama, 1955 †
Nucula paboensis (FOSSIL) A.A. Olsson, 1931 †
Ennucula pachydonta (B. Prashad, 1932)
Truncacila packardi (FOSSIL) Devjatilova, 1981 †
Acila paita (FOSSIL) A.A. Olsson, 1931 †
Lamellinucula pakistanica (FOSSIL) F.E. Eames, 1951 †
Leionucula palaioanaxea (FOSSIL) J.D. Stilwell, 1993 †
Leionucula palmeri (FOSSIL) Zinsmeister, 1984 †
Ennucula panamina (W.H. Dall, 1908)
Nucula papillifera K.H.J. Thiele& S.G.A. Jaeckel, 1931
Austronucula papuensis (W. Bergmans, 1978)
Nucula parisiensis (FOSSIL) G.P. Deshayes, 1860 †
Truncacila parva (FOSSIL) Devjatilova, 1981 †
Leionucula patagonica (FOSSIL) (R.A. Philippi, 1887 †)
Nucula paulula A. Adams, 1856
Truncacila pecticostata (FOSSIL) Kalishevich, 1969 †
Nucula peltella (FOSSIL) W.H. Dall, 1903 †
Nucula percrassa (FOSSIL) T.A. Conrad, 1856 †
Nuculoma peregrina (FOSSIL) (G.P. Deshayes, 1860 †)
Ennucula perforata (P.M. Rhind & J.A. Allen,1992)