OCCURRENCE AND COLLECTING OF MATERIAL 381 



number of times at the American Museum (where it is now preserved) 

 and elsewhere. A greatly reduced copy of it was published by Mook in 

 1914.2 



After the collecting of the material which formed the basis of the 

 above-mentioned reconstruction, Cope's collectors sent in more material. 

 This collecting was continued until 1880. 



GEOLOGICAL DE8CRIPTI0X OF THE CANYOy CITY DINOSAUR LOCALITY 



All the bones were found in the uppermost beds of the Morrison forma- 

 tion near Garden Park, about 8i4 miles north to northeast of Can3^on 

 City, Colorado. The Morrison in this locality is about 320 feet thick and 

 is a member of a triangular block of sedimentary rocks which is nearly 

 surrounded by the ancient crystallines. The apex of the triangle is toward 

 the north. The crystalline rocks bound the block on the east, north, and 

 west; toward the south the block merges into the sediments of the plains. 

 The block is partly faulted against the crystallines and partly folded 

 down alongside of them. Detailed information regarding the general 

 geology of the region is available in the Pikes Peak Folio^ of the United 

 States Geological Survey's Geological Atlas. 



The Morrison formation is composed lithologically of thin limestone 

 bands, sandstone beds, usually showing cross-bedding, but chiefly of fine 

 grits known as "joint-clays." This formation is one of great areal extent 

 and of comparatively small thickness. It has been interpreted as the 

 result of deposition of sediments, mainly by rivers, but partly by wind, 

 on a broad flat plain of rather low altitude. The conditions of its depo- 

 sition evidently provided broad areas of marshy country, with lakes, 

 interlacing streams, and flat interstream areas. Such conditions favored 

 the development of the Opisthocoelia and other branches of dinosaurs. 

 The age of the formation has been variously interpreted as Jurassic, Jura- 

 Cretaceous, and Comanchean. No opinion, however, upon that subject is 

 stated at the present time. The formation has recently been discussed by 

 Lee,* Mook,^ and Schuchert,^ to whose articles reference is made for fur- 

 ther information. 



2 Charles C. Mook : Notes on Camarasaurus Cope. Ann. New York Acad. Sci., vol. 

 xxiv, May 21, 1914, pp. 19-22, 1 fig. 



.3 Whitman Cross: Pikes Peak Folio: U. S. Geol. Survey, Geol. Atlas, Folio 7, 1894, 

 6 pp., 5 maps. 



* Willis T. Lee : Reasons for regarding the Morrison as an introductory Cretaceous 

 formation. Bull. Geol. Soc. Am., vol. 26, 1915, pp. 303-314. 



5 Charles C. Mook : A study of the Morrison formation. Ann. N. Y. Acad. Sci., vol. 

 xxvii, 1916, pp. 39-191, 94 figs., pi. vi. 



^ Charles Schuchert : Age of the American Morrison and East African Tendaguru for- 

 mations. Bull. Geol. Soc. Am., vol. 29, 1918, pp. 245-248. 



