4 ON THE GEOLOGY AND NATURAL HISTORY 
river, as well as some Cretaceous fossils from Sage creek. The Mammalian remains of 
this expedition were also studied by Dr. Leidy, and the invertebrate fossils by Drs. Evans 
and Shumard, and published in the Proceedings of the Academy of Natural Sciences at 
Philadelphia, and the Academy of Sciences of St. Louis. 
At the same time (1853), Mr. F. B. Meek and the writer, were employed by Professor 
James Hall of Albany, New York, to visit the Bad Lands of White river, for the purpose 
of making a collection of the Tertiary and Cretaceous fossils of that region. Many in- 
teresting and important facts were obtained during the expedition, in regard to the geo- 
logical structure of the country from Fort Pierre to Council Bluffs, which formed the 
basis of a paper read by Professor Hall before the Association for the Advancement of 
Science at the Providence meeting, in the summer of 1855. The Mammalian remains 
collected during this trip were placed in the hands of Dr. Leidy for examination, and the 
new species of Cretaceous fossils were investigated by Messrs. Hall and Meek, in an in- 
teresting memoir published in the Transactions of the American Academy of Arts and 
Sciences at Boston. A brief vertical section accompanied this memoir, showing the order 
of the superposition of the different Cretaceous beds. 
Subsequent to all these expeditions the writer again visited Nebraska and spent two 
years traversing various portions of that country; part of which time he was aided by Col. 
A. J. Vaughan, Indian Agent, and afterwards by Mr. Alexander Culbertson and other 
gentlemen of the American Fur Company. During this expedition he explored the Mis- 
sour to the vicinity of Fort Benton, and the Yellowstone to the mouth of Big Horn river, 
also considerable portions of the Bad Lands of White river and other districts not imme- 
diately bordering on the Missouri. The vertebrate remains collected by him, as may be 
seen by reference to the various papers by Prof. Leidy in the Proceedings of the Academy, 
embrace a larger number of species than all those previously known from that country, 
many of which belong to new and remarkable genera. 
Large collections of mollusca were also obtained from Cretaceous and Tertiary forma- 
tions, which have since been published by Mr. Meek and the writer, with remarks on the 
geology of different portions of the country, in several memoirs read before the Academy 
of Natural Sciences at Philadelphia. The geological results of the different expeditions 
along the Missouri and other portions of the Northwest, under the command of Lieutenant 
Warren, are embodied in the following report. 
In regard to the geology and natural history of Kansas and the southern portions of 
Nebraska, or the Platte country, important facts were secured by those enterprising ex- 
plorers, Cols. Long, Fremont, and Emory, and Capt. Stansbury. These have been al- 
ready published in their several reports. 
