926 BULLETIN 92, UNITED STATES NATIONAL MUSEUM. 



Ortonia Nicholson. See Cornulites Sehlotheim. 



Okusia Walcott. See Eoorthis subgenus Orusia. 



ORYGOCERAS Ruedemann. Genotype: Orthoceras cornuoryx Whitfield. 



Orygoceras Ruedemann, Bull. New York State Mus., 90, 1906, p. 449.— Grabau 

 and Shimer, N. A. Index Fossils, 2, 1910, p. 62. 



Orygoceras cornuoryx (Whitfield). 



Orthoceras cornu-oryx Whitfield, Bull. Amer. Mus. Nat. Hist., 1, 1886, p. 320, 



pi. 27, figs. 1, 2, 6.— Seely, Vermont State Geol. Rep., 7, 1910, pi. 56, fig. 3. 

 Orygoceras cornu-oryx Ruedemann, Bull. New York State Mus., 90, 1906, p. 



450, pi. 14, figs. 5-8, figs. 19-20. — Grabau and Shimer, N. A. Index Fossils, 



2, 1910, p. 63, fig. 1268. 

 Canadian (Beekmantown): Fort Cassin, Vermont; Valcour, New York. 



OTTAWACRINUS W. R. Billings. Genotype: O. typus W. R. Billings. 



Ottawacrinus W. 11. Billings, Ottawa Nat., 1, 1887, p. 49.— Miller, N. A. Gcol. 

 Pal., 1889, p. 265.— Bather, Ann. Mag. Nat. Hist., 6th ser., 5, 1890, p. 332, pi. 

 14, fig. 12. — Wachsmuth and Springer, Proc. Acad. Nat. Sci. Philadelphia, 

 1890, pp. 378, 380. — Bather, Treatise on Zool., pt. 3, Echinoderma, London, 

 1900, p. 178, fig. 96.— Springer, Mem. Geol. Surv. Canada, 15 P, 1911, p. 39.— 

 Bather, Bull. Victoria Mem. Mus., 1, 1913, pp. 1-10— Springer, Zittel- 

 Eastman Textb. Pal., 2d ed., 1913, p. 215. 



Ottawacrinus billingsi Springer. 



Ottawacrinus billingsi Springer, Mem. Geol. Surv. Canada, 15P, 1911, p. 40, 



pi. 4, figs. 1-3. 

 Trenton (Curdsville): Kirkfield, Ontario. 



Ottawacrinus typus W. R. Billings. 



Ottawacrinus typus W. R. Billings, Ottawa Nat., 1, 1887, p. 49.— Miller, N. A. 

 Geol. Pal., 1S89, p. 265, fig. 378.— Springer, Mem. Geol. Surv. Canada, 15P, 

 1911, p. 37, pi. 4, figs. 5-7.— Bather, Bull. Victoria Mem. Bull. 1, 1913, p. 



2, pi. 1. 

 Trenton (Curdsville): Hull, Quebec; Kirkfield, Ontario. 



Oxoplecia Wilson. See Triplecia subgenus Cliftonia Foerste. 



OXYDISCUS Koken. Genotype: Oxydiscus imitator Koken. 



Bellerophon, Cyrtolites, Porcellia, and Euomphalus (part) of authors. 

 Oxydiscus Koken, Neues Jahrb. Man., Geol. Pal., Beilageband, 6, 1889, p. 390; 

 ibid., 1898, p. 8; Die Leitfossilien, Leipzig, 1896, p. 100.— Ulrich and Sco- 

 field, Geol. Minnesota, 3, pt, 2, 1897, pp. 852-912.— Cumings, 32d Ann. Rep. 

 Dep. Geol. Nat. Res. Indiana, p. 951. — Grabau and Shimer, N. A. Index 

 Fossils, 1, p. 616. 



Oxydiscus acutus (?Sowerby) Billings. 



Bellerophon acutus Sowerby, Murehison's Sil. Syst., 1839, p. 643. — Billings, 



Cat. Sil. Fossils Anticosti, Geol. Surv. Canada, 1866, p. 18, 56. 

 Oxydiscus acutus Ulrich and Scofield, Geol. Minnesota, 3, pt. 2, 1897, p. 852 



(gen. ref.). 

 Gamachian (Ellis Bay): Gamache Bay, Anticosti. 



Oxydiscus argo (Billings). 



Bellerophon Argo Billings, Canadian Nat. Geol., 5, 1860, p. 167, figs. 12, 13; Geol. 

 Canada, Geol. Surv. Canada, 1863, p. 146, fig. 99a, b. 



