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XLIV. — On some Species of Orthocerata. 



By CHARLES STOKES, Eoq, F.G.S. 



Plates LIX. and LX. 



[Read June 6th, 1837.] 



Since the publication of Dr. Bigsby's paper on the geography and geo- 

 logy of Lake Huron, in the first volume of the 2nd series of this Society's 

 Transactions, in which some Orthocerata of peculiar forms are described, 

 I have seen and examined many specimens of that tribe of fossils from the 

 same place and from different parts of North America, as w^ell as from other 

 localities. 



Many of the American specimens of which I am about to speak derive ad- 

 ditional interest from the circumstances under which they were collected 

 during the expeditions of discovery by Sir John Franklin, Sir Edward Parry, 

 Dr. Richardson, the late Capt. Lyon and Capt. Back, and by Capt. Bayfield, 

 during his survey of the Lakes and the river St. Lawrence. The correspond- 

 ence in character of some of these Orthocerata with those of Lake Huron has 

 been slightly alluded to in the appendices to Sir John Franklin's second 

 journey and the Journal of Capt, Back, but 1 have thought it desirable to lay 

 before the Society a more detailed account of them, with figures of some of 

 the different species. 



It will be observed, that these American localities are widely separated 

 from each other, and are not parts of a continuous deposit ; but the agree- 

 ment in character of the limestone rock and of the fossils shows that they are 

 of the same geological age. 



For general remarks on the geology of these rocks, I beg to refer to the 

 appendices to the naratives of the expeditions above-mentioned. The object 

 of the present communication is to describe some species which indicate ge- 

 neric separations among the Orthocerata, and to call attention to some con- 

 siderations respecting the relations of the shells to the animals to which 

 they belonged. 



In the species of Orthoceras found at Thessalon Island, the peculiarity con- 



