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America, but most abundantly in the black transition 

 limestone, in the northern section of the country. 

 The richest locality, not only of this genus, but also 

 of the Calymene and the Asaph, is Trenton Falls, 

 on West Canada Creek, about 1 3 miles to the north 

 of Utica, in the state of New York. The following 

 extracts from the notes of Professor Renwick, which 

 accompany Dr. Dekay's account of the Isotelus, will 

 give some idea of this vast depository of the medals 

 of ancient zoology. West Canada Creek, is one of 

 the principal branches of the Mohawk River. At 

 Trenton Falls it has worn itself a passage through 

 the rock for the distance of nearly two miles, forming 

 a series of water falls; and has thus laid open to view 

 the strata to the depth of probably 300 feet. The 

 layers of the rock thus disclosed are nearly hori- 

 zontal, and of various thicknesses: they are composed 

 of limestone, with the exception of numerous thin 

 veins of argillaceous matter. The higher strata are 

 composed of carbonate of lime nearly pure, of a light 

 grey colour and crystalline structure. At greater 

 depths it is more compact and darker in colour, and 

 finally it appears quite black and highly foetid.* 



Animal remains are contained in every part of the 

 rock; besides several genera of trilpbites, we have 

 several species of orthocera. Encrinites and Fun- 

 gites Nautili Terebratulse and Producti, are quite 

 common. The favosites here are sometimes six 

 inches in diameter, and in such numerous columns, 



* See Annab of N. Y. Lyceum, vol. i. page 185. 

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