21S PALEONTOLOGY OF NEW YORK. 



from limestones of Lower Silurian age ; the«genus Ormoceras and the species 

 O. Bayfieldi, O. 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; O. mullilineatum, O. Trentonensis [=Cyrtoceras] and 

 Cameroceras Trentonensis, from the Trenton limestone ; Orthoceras aqualis, from 

 the Loraine shales = Hudson-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 O. annulatum of Sowbbbt. 



