GEOLOGY. 337 



us to suppose that those in our possession had been earned down the cur- 

 rent of a river, upon wlio.se banks the animal lived. 



The enormous size of this animal may be imagined when it is stated that 

 its thigh-bone is nearly one-third longer than that of a mastodon in the col- 

 lection of the Academy. 



There is also in the possession of the Academy a fragment of a thigh- 

 bone, found in the greensand of Xew Jersey some years since, and hitherto 

 uncharacterized, which now seems to have belonged to another much larger 

 individual of the Hadrosaurus genus than the one whose remains were dis- 

 covered by Mr. Foulke. 



Fragments of fossil wood found in proximity to the bones, have been 

 shown by Dr. Hammond, of Philadelphia, to belong to a species of conifer, 

 not differing materially in microscopic character from the pines that now 

 grow in the same locality. Various specimens of shells, all marine, were 

 also found so near, or interspersed with the bones and coniferous wood, as 

 to tend to prove that the animals and plants which they represent lived in 

 the vicinity of the shores which the Molhtsca inhabited, for these show that 

 they were deposited in a sediment totally and completely at rest. The most 

 tender and delicate forms remain without abrasion, and usually, in the case 

 of the bivalves, the two valves are attached. 



ON THE CRETACEOUS SYSTEM OF THE UNITED STATES. 



In connection with the foregoing description of the Hadrosaurus, the fol- 

 lowing paper, on the Cretaceous System of the United States, was read to the 

 Philadelphia Academy by Isaac Lea, Esq. 



Geological science is indebted to the late Professor Vanuxem for the 

 identification of the marl -beds of New Jersey and Delaware with the Creta- 

 ceous group of Europe; but it was not then known in either country that 

 there were so many subdivisions of the group, and the exact parallelism of 

 the greensand was not attempted to be traced. In 1828, Mr. Vanuxem, in 

 the Journal of the Academy, gave a tafiular view of the " relative geological 

 position " of the secondary, tertiary, and alluvial formations of the United 

 States, and also denned their geographical position, and stated that "this 

 bed (greensand) was argillaceous, and contained greenish particles analo- 

 gous to those which are found in the greensand, or chalk, of Europe," and 

 that it was "characterized by six genera, viz., Terebmtida, Gryphcea, Exo- 

 gyra, Ammonites, Baculites, and Belemnitrs." These views of Professor Van- 

 uxem were subsequently confirmed in various papers, published by Dr. 

 Morton and other geologists, and from year to year new explorations have 

 tended to demonstrate the vast extent of the Cretaceous formation in the 

 United States east of the Rocky Mountains. 



The Cretaceous Formation commences at Martha's Vineyard, in Massa- 

 chusetts, is largely developed in New Jersey, and is found in Delaware, 

 Maryland, Virginia, and the Carolinas. In Georgia, it is more largely devel- 

 oped. Here, sweeping round the inferior strata, the Primary, Silurian, and 

 Carboniferous masses, it continues in a very enlarged band in a northerly 

 direction, through Alabama, Mississippi, and Tennessee, to near the mouth 

 of the Ohio River. Crossing the Mississippi River, it descends to the south- 

 west, through Arkansas, where, on the upper waters of the Red River, it 

 expands to the north, through Nebraska Territory, far into the British Pos- 

 sessions east of the Rocky Mountains, embracing the head waters of the 



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