Orthoceras nicolleti (FOSSIL) A.H. Clarke †
Orthoceras niissoni (FOSSIL) Boll, 1857 †
Orthoceras novator (FOSSIL) Barrande, 1868 †
Striatocycloceras obliquum (FOSSIL) (d'Eichwald, 1860 †)
Orthoceras oehlerti (FOSSIL) C. Gemmellaro, 1889 †
Orthoceras orientale (FOSSIL) Fliegel, 1901 †
Orthoceras oryx (FOSSIL) Whidborne †
Orthoceras oweni (FOSSIL) Ulrich, 1894 †
Orthoceras pendens (FOSSIL) Blake †
Orthoceras perroti (FOSSIL) A.H. Clarke †
Orthoceras pertinens (FOSSIL) Blake †
Orthoceras planoconvexum (FOSSIL) J.W. Hall †
Orthoceras planodorsatum (FOSSIL) R.P. Whitfield †
Orthoceras primaevum (FOSSIL) (Forbes) †
Orthoceras progressum (FOSSIL) Ruedemann, 1906 †
Trematoceras pulchellum (FOSSIL) (J. Von Hauer, 1849 †)
Orthoceras pulchrum (FOSSIL) Barrande, 1868 †
Orthoceras punjabiense (FOSSIL) L. Waagen, 1879 †
Orthoceras pusgillense (FOSSIL) Foord †
Orthoceras rachidium (FOSSIL) de Koninck, 1863 †
Orthoceras regularis (FOSSIL) (Schlotheim, 1820 †)
Pseudospyroceras reticulum (FOSSIL) Kröger, 2008 †
Tibichoanoceras riphaeum (FOSSIL) (P.A. Zhuravleva, 1978 †)
Orthoceras robertsii (FOSSIL) Whidborne †
Striatocycloceras romingeri (FOSSIL) (Foerste, 1932 †)
Trematoceras salinarium (FOSSIL) (J. Von Hauer, 1846 †)
Trematoceras sandlingense (FOSSIL) (Mojsisovics, 1873 †)
Orthoceras scabridum (FOSSIL) Angelin, 1880 †
Ctenoceras schmidti (FOSSIL) Noetling, 1884 †
Tenuitheoceras secretum (FOSSIL) M.A. Frey & al., 2014 †
Orthoceras sericatum (FOSSIL) Barrande, 1868 †
Orthoceras shastense (FOSSIL) A. Hyatt & Smith, 1905 †
Orthoceras siculum (FOSSIL) C. Gemmellaro, 1889 †
Orthoceras spissiseptum (FOSSIL) Dwight, 1884 †
Orthoceras stokesi (FOSSIL) Barrande, 1868 †