THE EETUEN MAECH. 37 



Tail and Red Cloud, the expedition returned by the agency road to Fort, 

 Laramie. 



The geological features of our return route from the White River to 

 Fort Laramie are very uniform, the underlying rocks belonging entirely 

 to the White River Tertiary. The typical bad-land arenaceous clays, 

 destitute of vegetation, already mentioned as lying between the White and 

 Cheyenne Rivers, are the very lowest members of the White River group, 

 while the strata found on the immediate banks of the White River, and 

 especially in the upper portion of its valley, are more recent and belong 

 to the upper part of the series. Their equivalents probably form the under- 

 lying rocks on the line of our outward march. Though the whole country 

 bordering the White River is commonly known as the Bad Lands, the term 

 is more properly applied solely to the lower clays, which weather in the 

 fantastic shapes already mentioned, and which contain such abundant 

 remains of vertebrate animals. 



Our march on White River took us across the scene of the distinguished 

 paleontological discoveries of Dr. Hayden and Professor Marsh, a district 

 which their labors and those of Dr. Leidy have rendered as famous as the 

 Sivalik Hills of India; but it was not our privilege to linger. 



Between the White River and the Platte the Tertiary is very little 

 denuded, and presents all the aspects of the geology of our outward route. 



