586 REPORT OF NATIONAL MUSEUM, 1904. 



Cretaceous formation : 



5. Arenaceous clay passing into argillo-calcareous sandstone. 80 feet. 



4. Plastic clay with calcareous concretions containing numerous fossils. 250 to 



350 feet. 

 This is the principal fossiliferous bed of the Cretaceous formation upon the Upper 



Missouri. 

 3. Calcareous marl, containing Ostrea congesta, scales of fishes, etc. 100 to 150 



feet. 

 2. Clay containing few fossils. 80 feet. 

 1. Sandstone and clay. 90 feet. 

 Buff-colored magnesian limestone of the Carboniferous period. 



In the following- spring - (1851) Doctor Hayden again ascended the 



Missouri River, this time parti} 7 under the auspices of the American 



Fur Company. He spent two years on this expedition, during which 



time he visited the various portions of the Upper 



Hayden 's Work on . , . . 



the Upper Missouri, Missouri, being without any other means than what he 

 earned or secured in various ways as he went along, 

 and dependent even for subsistence entirely on such friends as he met 

 in the country, among whom were Col. A. J.«Vaughan, the Indian 

 agent, and Mr. Alexander Culbertson, of the American Fur Company. 



He traversed the Missouri River to Fort Benton and the Yellow- 

 stone to the mouth of the Big Horn, and also considerable portions of 

 other districts not immediately bordering on the Missouri. As the 

 boats of the fur company had to be towed in ascending the river, the 

 progress was necessarily slow. The time thus occupied by the boats 

 was utilized by Hayden on the shores, and as a result he traversed a 

 considerable portion of the journey on foot. 



The vertebrate remains collected on this trip were, as in a previous 

 case, described by Doctor Leidy, mainly in papers read before the 

 Academy of Natural Sciences of Philadelphia, while the invertebrates 

 were described by Doctor Hayden himself in connection with Professor 

 Meek. The collections, which were deposited partly with the Academy 

 of Science of St. Louis and partly with the Academy of Natural 

 Sciences of Philadelphia, contained a larger number of species than all 

 those previously known from that country, many of them being new 

 and of a remarkable character. 



Early in 1856 Hayden returned to St. Louis, and on February 15 



of that year received from Lieut. G. K. Warren, of the U. S. Corps 



of Topographical Engineers, an offer to report upon the Sioux country. 



This report was made, and in May of the same year 



Hayden with x . , , . ... . . ,, 



warren in the Sioux \\ arreii appointed him one of his assistants in the 



Country, 1856. . r „ . T . 



exploration of the Yellowstone River and the Missouri 

 River from Fort Pierre to a point 60 miles north of the mouth of the 

 Yellowstone. 



The held work of this expedition began on June 28, the party 

 returning to Fort Pierre on October 22, and reaching Washington in 



