NEL. ORT.] 



CEPHALOPODA. 



445 



subsulcatm, Phillips, 1836, Geo. York. Not 



clearly identified in this country. 

 sulcatus, see Trematodiscus sulcatus. 

 trigonus, see Trematodiscus trigonus. 

 trisulcatus, see Trematodiecus trigulcatus. 

 tyrans, Billings, 1859, Can. Nat. and Geo., 



vol. 4, p. 465, Chazy Gr. 

 versutus, Billings, 1865, Pal. Foss., vol. 1, 

 p. 259, Quebec Gr. Type of Hyatt's 

 genus Litoceras. 



winslowi, see Temnochilus winslowi. 

 Nelimenia incognita, Castelnau, 1843, Syst. 

 Sil., p. 33. Probably a fragment of 

 Phragmoceras or Oncoceras. 

 ONCOCERAS, Hall, 1847, Pal. N. Y., vol. 1, p. 

 196. [Ety. onkos, swelling ; keras, horn.] 

 Curved, aperture constricted; lower 

 part of the body chamber, and upper 

 part of septate portion ventricose ; ab- 

 ruptly contracted to- 

 ward the apex ; siphun- 

 cle dorsal ; septa plane, 

 nearly flat, slightly ele- 

 vated on the dorsal 

 margin. Type O. con- 

 strictum. 



abruptum, Hall, 1861, Rep. 

 of Progr. Wis., p. 44, 

 Trenton Gr. 



alceus, Hall, 1861, Rep. of 

 Progr. Wis., p. 46, Chazy 

 and Black Riv. Grs. 

 amator, Billings, 1866, 

 Catal. Sil. Foss. Antic., 

 p. 59, Clinton Gr. 

 brevicurvatum, Whitfield, 1880, Ann. Rep. 

 Geo. Sur. Wis., p. 59, and Geo. Wis., 

 vol. 4, p. 234, Trenton Gr. 

 constrictum, Hall, 1847, Pal. N. Y., vol. 1, 



p. 197, Black Riv. and Trenton Grs. 

 dilatatum, Hall, 1860, 13th Rep. N. Y. 



Mus. Nat. Hist., p. 105, Ham. Gr. 

 expansum, Hall, 1852, Pal. N. Y., vol. 2, 



p. 337, Coralline limestone, 

 futile, Billings, 1866, Catal. Sil. Foss. 



Antic., p. 59, Clinton Gr. 

 gibbosum, Hah, 1852, Pal. N. Y., vol. 2, 



p. 13, Medina sandstone, 

 lycus, Hall, 1861, Rep. of Progr. Wis., p. 



45, Chazy and Black Riv. Gr. 

 mummiforme, Whitfield, 1880, Ann. Rep. 

 Geo. Sur. Wis., p. 58, and Geo. Wis., 

 vol. 4, p. 232, Trenton Gr. 

 orcas, Hall, 1861, (Cyrtocerasorcas,) Rep. 

 of Progr. Geo. Sur. of Wis., p. 42, Niag- 

 ara Gr. 

 ovoides, Hall, 1859. Pal. N. Y., vol. 3, p. 



342, Low. Held. Gr. 



pandion, Hall, 1861, Rep. of Progr. Wis., 

 p. 45, and Geo. Wis., vol. 4, p. 233, 

 Chazy and Black Riv. Grs. 

 pettiti, Billings, 1866, Catal. Sil. Foss. 



Antic., p. 86, Niagara Gr. 

 plebeium, Hall, 1861, Geo. Rep. Wis., p. 



44, Trenton Gr. 

 subrectum, Hall, 1852, Pal. N. Y., vol. 2, 



p. 94, Clinton Gr. 



teucer, Billings, 1866, Catal. Sil. Foss. 

 ' Antic., p. 86, Niagara Gr. 



FIG. 748. Onco- 

 ceras constric- 



tum - 



thales, Billings, 1866, Catal. Sil. Foss. 

 Antic., p. 87, Niagara Gr. 



vasiforme, Dwight, 1884, Am. Jour. Sci. 

 and Arts, 3d ser., vol. 27, p. 257, Calcif- 

 erous Gr. 



OKMOCERAS, Stokes, 1840, Trans. Geo. Soc., 

 2d ser., vol. 5, p. 709. [Ety. ormos, a 

 chain or necklace ; keras, horn ; from 

 the appearance of the sip h uncle.] Ex- 

 ternally like Orthoceras, and dis- 

 tinguished only by having the siphun- 

 cle constricted within each chamber in- 

 stead of at the place of union with the 

 septa. Types 0. backi, and O. bayfieldi. 



backi, Stokes, 1840, Trans. Geo. Soc., 2d 

 ser., vol. 5, p. 709, Clinton Gr. 



bayfieldi, Stokes, 1840, Trans. Geo. Soc., 

 2d ser., vol. 5, p. 709, Clinton Gr. 



ere bri sep- 

 tum, Hall, 

 1847, Pal. 

 N. Y., vol. 

 1, p. 313, 

 Hud. Riv. 

 Gr. 



gracile, Hall, 

 1847, Pal. 

 N. Y., vol. 



1, p. 58, 

 Black Riv. 



t* r - 



remotisep- 



tum, Hall, p IG . 749. Ormoceras bayfleldi. 



1850, 3d 



Rep. N. Y. Mus. Nat. Hist, p. 181, 



Trenton Gr. 

 tenuifilum, Hall, 1847, Pal. N. Y., vol. 1, 



p. 55, Black Riv. and Trenton Gr. 

 tenuifilum var. distans, Hall, 1847, Pal. 



N. Y., vol. 1, p. 58, Black Riv. Gr. 

 vertebratum, Hall, 1852, Pal. N. Y., vol. 



2, p. 94, Clinton Gr. 



whitii, Stokes, 1840, Trans. Geo. Soc., 2d 



ser., vol. 5, p. 709, Clinton Gr. 

 ORTHOCERAS, Breynius, 1732, Dissertatio 

 physica de Polythalamiis. [Ety. orthos, 

 straight; keras, horn.] Shell conical, 

 straight, or nearly so ; body chamber 

 large, behind which the shell is com- 

 posed of numerous chambers separated 

 by convex, transverse septa, with simple 

 edges, at right angles to the longer axis 

 of the shell; siphuncle central, sub- 

 central or eccentric, cylindrical or di- 

 lated in the chambers ; surface smooth 

 or transversely, or longitudinally stri- 

 ated, or furrowed. Typical O. breynii, 

 0. annulatum, and 0. striatum. 



abnorme, Hall, 1867, 20th Rep. N. Y. 

 Mus. Nat. Hist, p. 415, Niagara Gr. 



abruptum, Hall, 1852, Pal. N. Y., vol. 2, 

 p. 97, Clinton Gr. 



acicula, Hall, see Coleolus acicula. 



aciculoides, Clarke, 1885, Bull. U. S. Geo. 

 Sur., No. 16, p. 51, Chernung Gr. 



aculeatum, Swallow, 1858, Trans. St. Louis 

 Acad, Sci., vol. 1, p. 200, Coal Meas. 



jegea, Hall, 1862, 15th Rep. N. Y. Mus. 

 Nat. Hist,, p. 80, Ham. Gr. 



