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Dr. Morton notes the generic accordance of the Testaceous Mol- 

 lusca on the east and west shores of the Atlantic; but indepen- 

 dently of genera, there are at least twenty-four species common 

 to both. In like manner some identities have been traced in 

 the tertiary deposits of Europe and America. The Peden quin- 

 quecostatus in particular occurs equally in the cretaceous group on 

 both sides the Atlantic; nor is the analogy confined toTestaceaj it 

 extends to the Saurian reptiles. The animals whose remains are 

 found in chalk formerly inhabited the seas of the two continents, 

 and whatever cause bared the eastern, appeal's to have acted simul- 

 taneously on the western mass; not a rush of currents, but a subsi- 

 dence or elevation. 



In the county of Onondago, in New York, is a lacustrine depo- 

 sit still forming, in which thousands of tons might be obtained of 

 bleached shells. The shells at the mouth of the Potomac river, be- 

 longing to the newer Pliocene beds, retain their colours ; twenty- 

 nine of the species are the same with those which now live, and of 

 these there are seven only which are not known to inhabit the coast 

 of America. 



From the upper marine deposit of Dr. Morton, which corre- 

 sponds to the lower tertiary of Mr. T. A. Conrad, and to the older 

 pliocene of Mr. Lyell, numerous specimens were exhibited to us in 

 the course of last session by Mr. Finch. Of fifty-six species of 

 shells observed by Mr. Conrad in this deposit, which extends through 

 Maryland, Virginia, and the county of Cumberland, in New Jersey, 

 one third still exist on the coast of America, but some species in a 

 more southern latitude than that in which they are found fossil. 



The Miocene beds, if they occur, have hitherto escaped detec- 

 tion. The Eocene, the middle tertiary of Mr. Conrad, which in En- 

 gland is known as the London clay, and in France as coarse lime- 

 stone, assumes in America the character of siliceous sand, and in 

 that form has been traced in a north-eastern and south-western di- 

 rection from Alabama, through South Carolina, Georgia, and Flo- 

 rida, as far as the Gulf of Mexico. Two hundred and nineteen 

 species of shells found in this deposit have been described by 

 Mr. Lea, but among them all, there is perhaps not one entirely analo- 

 gous to any living species. Several of these shells belong to genera 

 unknown upon the coast of America, some to genera found fossil 

 in Europe, some to genera entirely new. It may be doubted whe- 

 ther any of the species correspond with any of the eocene fossils 

 of Europe, but the number of turreted shells and generic resem- 

 blance satisfactorily establish the epoch to which they belong. 



It appears from the observations of M. Dufrenoy that in the 

 chalk of the Pyrenees fifty species, in a list of about two hundred, 

 have the character of tertiary shells. A corresponding gradation 

 in the fossil contents of the tertiary and cretaceous formations is 

 observable in America. The Chalk, or rather the Chalk-Marl, of the 

 new continent occupies large tracts in New Jersey, Delaware, and 

 Alabama, and contains among other organic remains teeth of the 



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