/. Hall on the Cretaceous Strata of the United States, 77 



several Pacific Railroad surveys liave shown tlie occurrence of 

 cretaceous fossils at various points farther to the south, and at 

 intervals which indicate a continuation of the formation from the 

 Missouri river to New Mexico. More recently Dr, Evans, who 

 had previously visited this region as assistant in the geological 

 survey of Dr. Owen, has collected, and, with Dr. B, F. Shumard, 

 has described several new cretaceous species from the same region. 



In 1853, Messrs, F. B. Meek and F. Y. Ilaj^den made an ex- 

 tensive collection of the fossils of the cretaceous formation upon 

 the Missouri river in Nebraska; and among these somewhat 

 more than thirty new species, a number equal to all the creta- 

 ceous species before known as occurring in that region. These 

 species were described by the writer in connexion with Mr. 

 Meek, in the Memoirs of the American Academy of Arts and 

 Sciences.* A section of the cretaceous and tertiary strata of 

 the Missouri river and the !Mauvaises Terres, compiled from the 

 notes of Mr. Meek, made upon the ground, and verified by sub- 

 sequent examination of the fossils, likewise accompanied the pa- 

 per just noticed, on page 405 of the same volume. 



The order of succession among the beds constituting the cre- 

 taceous formation and their lithological character there estab- 

 lished are as follows : 



SECTIOX OF THE MEMBERS OF THE CRETACEOUS FORMATIOX, AS OBSERVED 





ON THE MISSOURI RIVER BELOW FORT PIERRE, AND THENCE WESTWARD, 

 INCLUDING THE TERTIARY BEDS OF THE MAUVAISE8 TERRES. 



III. Tertiary. 



InJurated clays, beds of sandstone, conglomerate, limestone, etc., contain- 

 ing remains of Mammalia, and Chelonia, with a few species of fresb 

 water shells. 



IL Cretaceous Formation or Nebraska, 



6. Arenaceous clay parsing into argillo-calcareous sandstone, 80 feet 

 thick. 



' "^d 4. Plastic clay with calcareous concretions, containing numerous fossils, 



c — -^ 1 5> 



"^ ,!: i » o*^ 250 to 300 feet thick. (This is the principal fossiliferous bed of the 





gu cretaceous formation upon the upper Missouri.) 



2« 3. Calcareous marl, containing Ostrea congesta, Tnocerami^ jirohlemat- 

 *■* icns,\ scales of fishes, &c., 100 to 150 feet thick. 





j^< 2. Clay containing few fossils, 



1. Sandstone and clay, 90 feet. The probable equivalent of Nos. 1 and 

 2, of the New Jersey section, 



L Caeboniferocs Formation. 



The sandstone No, 1, of section rests upon buff-colored magnesian lime- 

 stone of the upper Carboniferous period. 



* Descriptions of new species of Fossils from the Cretaceous formation of Ne- 

 braska, by James Hall and F. B. Meek. Memoirs of the American Acadeniy of 

 Arts and Sciences, vol v, new series. 



f In a subsequent exploration of this region, Dr. IlayJen discovered Inocera^/iiu 

 problnnaticus in thU bed, corresponding in all respects with tliose collected by 

 Mr. Nicollet, and in precisely the same condition?? and in a rock identical with that 



