•0 PALAEONTOLOGY OF NEW-YORK. 



nent, and characterized over a much wider area by its marine animal 

 remains, than by the remains of terrestrial vegetation in the present 

 known areas of the Coal measures on the east of the Rocky mountains. 



With the termination of the Coal measures of the eastern part of 

 our continent, ceased the sedimentary deposits, which for so long a 

 period accumulated along the line of the Appalachian chain. At this 

 time or subsequently, and before any deposits in direct sequence had 

 been made, the whole eastern region appears to have emerged from the 

 ocean. 



It is true that we still find sediments of a newer era on the eastern 

 flanks of this mountain range, in Nova-Scotia, in the Connecticut 

 river valley, and in New-Jersey, Pennsylvania, Virginia and North- 

 Carolina, which have a trend in the same direction ; but it is not yet 

 proved, so far as I know, that the source of these formations was the 

 same as that of the older deposits, and they are not in direct sequence. 

 Along this line these accumulations, which are somewhat disconnected, 

 may have been influenced by proximity to coast lines, and not by any 

 strongly marked ocean current in that direction. 



The accumulations of the Coal period were the last that have given 

 form and contour to the eastern side of our continent, from the Gulf 

 of St. Lawrence to the Gulf of Mexico. And as we have shown thai 

 the great sedimentary deposits of successive periods have followed 

 essentially the same course, parallel to the mountain ranges, we very 

 naturally inquire : What influence has this accumulation had upon the 

 topography of our country ? and is the present line of mountain eleva- 

 tion, from northeast to southwest, in any manner connected with this 

 original accumulation of sediments ? 



I have all along shown that the sedimentary deposits are greatly 

 thicker in the eastern than in the western localities, and that for the 

 most part they are extremely poor in calcareous matter ; while gene- 

 rally the limestone formations, individually and in the aggregate, are 

 thicker at some distance west of the line of greatest sedimentary 

 accumulations. 



