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76 71 Hall on the Cretaceous Strata of the United States, 



doubt as to the close similarity of the formation there developed, 

 with the beds in New Jersey from which a large part of the fos- 

 sils described by Dr. Morton were obtained. The calcareous 

 part of the formation in Alabama acquires a far greater develop- 

 ment than in New Jersey, and appears to be there the principal 

 repository of the fossils of this period. 



It is now more than fifty years since Messrs. Lewis and Clarke, 

 in their expedition to the Columbia River, brought from the 

 Great Bend of the Missouri River some fossils which were after- 

 wards identified by Dr. Morton as belonging to the cretaceous 

 formation ; and to beds of the same age as the marl or ferrugi- 

 nous sand of New Jersey, Delaware and Alabama. Subsequently 

 Mr. Nuttall brought some species from the same locality, Dr, 

 Morton in his Synopsis (1834) acknowledges the receipt of 

 Gryph^a Pitcheri^ and other cretaceous fossils of great interest 

 from the plains of Kiamesha in Arkansas^ from Dr. Z. Pitcher of 

 the United States Army. Dr. Morton also mentions other fos- 

 sils from the falls of Verdigris river in the same territory. 



It is nearly twenty years since Mr. Nicollet first visited and 

 explored the country about the sources of the Mississippi and 

 some parts of the Missouri river, as far up as Fort Pierre. The 

 collections made by this gentleman enabled Dr. Morton to desig- 

 nate about sixteen species of cretaceous fossils, half of which were 

 regarded as common to that region, New Jersey and Alabama. 



Mr. Nicollet in his report has given the following section of 

 the beds of the cretaceous formation upon the upper Missouri, ': 



D. "A plastic clay deposit, about 200 feet thick, divided into two equal 



parts by a stratum of carbonate of lime in nodules. 



C. " A ferruginous clay, of a yellowish color, containing masses resem- 

 bling septaria and seams of selenite." 



B. "A calcareous marl, generally from 30 to 40 feet thick." 



A. "Argillaceous lime|(:one, containing Inoceramus Barahini [?] in 



great numbers and very much compressed^ and so arranged as 

 to give the rock a slaty appearance" (at Dixon^s Bluff).* * 



The importance of these divisions does not appear to have 

 been fully appreciated, or the collection of fossils was not suffi- 

 cient to establish the restriction of species within the limits thus 

 indicated. 



In the mean time the explorations of Lieut. Fremont, of Lieut. 

 Abort, ^ of Capt. Stansburj and others, and more extended ex- p 



aminations made under the direction of Dr. D. D. Owen, in his 

 geological survey of. the Chippewa Land District have brought 

 to light other cretaceous species from this region ;f while the 



* The species of Inoceramus in Mr. Nicollet's collection, in a condition here de- 

 scribed, was subsequently identified by me as the same with that brought by C&pt. % 

 Fremont from the 8moky Hill River. (See Report, p. 310.) 



f In his report Dr. Owen does not notice the subdivisions of Mr. Nicollet's sec- 

 tion ; and the cretaceous species figured and described appear all to have been de- 

 rived from a single bed of die formation. 



