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PALEONTOLOGY OF NEW YORK. 



the present time. Two of the most abundant, and, so far as known, widely 

 distributed species, the T. gyracanthus and T. attenuatus, occur in very dissimilar 

 deposits — one of them being in a limestone, while the other occurs in an 

 arenaceous or semi-argillaceous formation. These, in their respective horizons, 

 can be traced for the distance of more than three hundred miles in a northeast 

 and southwest direction, while they have a very limited extension to the 

 westward. Since, as a rule, these fossils occur in limestone or in semi- 

 calcareous deposits, it seems a little remarkable that neither T. attenuatus or 

 T. spiculus should be found in the western extension of their respective 

 formations, in which direction the sediments become more calcareous. In the 

 single example of T. scalariformis, we find a greatly increased number of 

 individuals in a westerly direction, as far as Ohio, but this is strictly along 

 the trend of the limestone formation. 



The following tabular arrangement of species described under the generic 

 name of Tentaculites will show their distribution in the American Palaeozoic 

 rocks: 



