Ch. xvil] cretaceous rocks. 339 



fore, is not small, when we reflect that the part of the United States 

 where these strata occur is between 3000 and 4000 miles distant from 

 the chalk of Central and Northern Europe, and that there is a differ- 

 ence of ten degrees in the latitude of the places compared on oppo- 

 site sides of the Atlantic* 



Fish of the geuera Lamna, Galeus, and Carcharodon are common 

 to New Jersey and the European cretaceous rocks. So also is the 

 genus Jfosasaitrits among reptiles. The vertebra of a Plesiosaurus, a 

 reptile known in the English chalk, had often been cited on the au- 

 thority of Dr. Harlan as occurring in the cretaceous marl, at Mullica 

 Hill, in New Jersey. But Dr. Leidy has since shown that the bone 

 in question is not saurian but cretaceous, and whether it can truly lay 

 claim to the high antiquity assigned to it, is a point still open to dis- 

 cussion. The discovery of another mammal of the seal tribe (Steno- 

 rhynclius vetus, Leidy), from a lower bed in the cretaceous series in 

 New Jersey, appears to rest on better evidence.f 



From New Jersey the cretaceous rocks extend southward to North 

 Carolina and Georgia, cropping out at intervals from beneath the ter- 

 tiary strata, between the Appalachian Mountains and the Atlantic. 

 They then sweep round the southern extremity of that chain, in Ala- 

 bama and Mississippi, and stretch northward again to Tennessee and 

 Kentucky. They have also been traced far up the valley of the Mis- 

 souri, as far north as lat. 48°, or to Fort Mandan ; so that already the 

 area which they are ascertained to occupy in North America may 

 perhaps equal their extent in Europe, and exceeds that of any other 

 fossiliferous formation in the United States. So little do they resem- 

 ble mineralogically the European white chalk, that in North America, 

 limestone is upon the whole an exception to the rule ; and, even in 

 Alabama, where I saw a calcareous member of this group, composed 

 of marl-stone, it was more like the English and French Lias than any 

 other European secondary deposit. 



* See a paper by the Author, Quart. Journ. Geol. Soc, vol. i. p. 79. 



\ In the Principles of Geology, ninth ed. p. 145, I cited Dr. Leidy of Philadel- 

 phia as having described (Proceedings of Acad. Nat. Sci. Philad., 1851) two species 

 of cetacea of a new genus which he called JPriscodelphimes, from the greensand of 

 New Jersey. In 1853 I saw the two vertebras at Philadelphia on which this new 

 genus was founded, and afterwards, with the aid of Mr. Conrad, traced one of them 

 to a Miocene marl pit in Cumberland County, New Jersey. The other (the Plesio- 

 saurus of Harlan), labelled " Mullica Hill" in the Museum, would no doubt be an 

 upper cretaceous fossil, if really derived from that locality, but its mineral condition 

 makes the point rather doubtful. The tooth of Stenorhynchus vetus figured by 

 Leidy from a drawing of Conrad's (Proceed, of Acad. Nat. Sci. Philad., 1853, p. 

 377), was found by Samuel R. "Wetherill, Esq., in the greensand l£ mile southeast 

 of Burlington. This gentleman related to me and Mr. Conrad, in 1853, the circum- 

 stances under which he met with it, associated with Ammonites placenta, Ammon- 

 ites Delawarensis, Trigonia thoracica, &c. The tooth has been mislaid, but not 

 until it had excited much interest and had been carefully examined by good zoolo- 

 gists. 



