1. obductum
    [Kosmoceras obductum (M)]
  2. obductum
    [Kosmoceras obductum (M)]
  3. oblique-strangulatus
    [Protetragonites oblique-strangulatus]
  4. obliquus
    [Scaphites obliquus]
  5. obliquus
    [Scaphites aff. obliquus]
  6. obliquus
    [Scaphites obliquus]
  7. obscurus
    [Pseudoneoptychites obscurus forme andinus]
  8. obscurus
    [Pseudoneoptychites obscurus morphe difficilis]
  9. obscurus
    [Pseudoneoptychites obscurus forme intermedius]
  10. obtusum
    [Asteroceras obtusum]
  11. ochetonotus
    [Euhoplites ochetonotus]
  12. oegir
    [Euaspidoceras oegir (M)]
  13. oehlerti
    [Subpulchellia oehlerti]
  14. oehlerti
    [Subpulchellia oehlerti]
  15. ohmi
    [Pseudothurmannia ohmi (M)]
  16. oldhami
    [Pachydiscus (P.) oldhami]
  17. onilahyense
    [Barroisiceras onilahyense]
  18. onilahyense
    [Barroisiceras onilahyense]
  19. oolithicum
    [Lissoceras oolithicum]
  20. oppeli
    [Oxycerites oppeli]
  21. orbignyanum
    [Chondroceras orbignyanum]
  22. orbignyi
    [Normannites orbignyi (m)]
  23. orbignyi
    [Spiroceras orbignyi (M)]
  24. orbis
    [Oxycerites orbis (M)]
  25. otsukai
    [Eubostrychoceras (E.) otsukai]
  26. otsukai
    [Eubostrychoceras (E.) otsukai morphe boulei]
  27. ovale
    [Sonninia (Fissilobiceras) ovale]
  28. oxyptycha
    [Collotia oxyptycha forme paronai (m)]