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PALAEONTOLOGY OF NEW YORK. 
from limestones of Lower Silurian age; the genus Ormoceras and the species 
0. Bayfieldi, 0. Backii, and 0. Whitei, the last three named species being from 
Drummond Island; also, Huronia Portlocki, from the same locality (On some 
species of Orthocerata: Trans. Geol. Soc. London, 2d series, vol. 5). 
In 1838 Prof. Gerard Troost proposed the genus Conotubularia for certain 
forms of Orthoceras (which are, in part, referred to Endoceras), and described 
the following species from the Lower Silurian: Conotubularia Brongniarti, C. 
Cuvieri, C. Defranci and C. Goldfussi (Mem. Soc. Geol. de France , T. III). 
In the same year Mr. T. A. Conrad described 0. constrictum, from the Ham¬ 
ilton group [Rep. Pal. Dept. N. Y. Geol. Survey). 
In 1839 Mr. J. de C. Sowerby described 0. imbricatum and 0. virgatum 
from the Ludlow and Wenlock formation (Murch. Silur. Syst.). These species 
have been identified with forms in the Niagara group of North America. 
In 1840 Dr. D. D. Owen described and illustrated Orthoceras marginale, Owen, 
from the Upper Magnesian limestone; 0. undulatum* 0., from the “Magnesian 
Cliff limestone; ” and figured an Orthoceras [—Endoceras], “from the substrata 
of the Blue and Gray limestones” of Iowa and Wisconsin. He also designated 
Orthoceras annulatum ? and Actinoceras, with double siphuncle, as occurring in 
the “coralline beds ” of the Magnesian Cliff limestone; and cited Orthoceras 
anellum, Conrad, from the Blue and Gray limestones (Report on the Geol. Explor. 
of part of Iowa, Wisconsin and Illinois). [Communicated to the General Land 
Office in 1840, published in 1844.] 
In 1842 Mr. Conrad published descriptions of the genera Cameroceras 
and Diploceras [= Endoceras, Hall, 1847], with the species Cameroceras Tren- 
tonensis and Diploceras Vanuxemi (Jour. Acad. Nat. Sci. Phila., vol 8, pt. 2). 
Dr. E. Emmons published Orthoceras multicameratum (Conrad, in ms.), from 
the Birdseye limestone; 0. multilineatum, 0. Trentonensis [=Cyrtoceras] and 
Cameroceras Trentonensis, from the Trenton limestone; Orthoceras cequalis, from 
the Loraine shales = Iludson-river group; and illustrated other forms of Ortho¬ 
ceras from the Trenton limestone, without specific designation (Geol. Surv. of 
N. Y., Second Dist.). 
* O. undulatum in this place is apparently a cast of 0. annulatum of Sowerby. 
