XXII INTRODUCTORY REMARKS. 



to have noticed, as a separate subdivision, the Fort Benton group, and 

 apparently subdivided the Niobrara beds into two formations; while the 

 Dakota group he passed unnoticed, probably supposing it to be Carboniferous, 

 and the Fox Hills group be apparently did not see. 



In 1849, Dr. John Evans, one of Dr. Owen's assistants in the United 

 States Geological Survey of portions of the Northwestern States and Terri- 

 tories; ascended the Missouri to Fort Pierre, and thence crossed the country 

 to the Bad Lands, on White River, Nebraska, during which journey he not 

 only collected many interesting vertebrate remains from the White River 

 Tertiary beds, but also brought a number of Cretaceous invertebrate fossils 

 from beneath the Tertiary rocks on Sage Creek and other localities. These 

 Cretaceous fossils were figured and described by Dr. Owen in his final 

 report in 1852.* 



In 1853, the writer, assisted by Dr. Hay den. was sent by Professor 

 Hall on an expedition to the Bad Lands, Nebraska, mainly for the purpose 

 of procuring a collection of the Tertiary vertebrate remains so abundant 

 there. This expedition brought a valuable collection of these Tertiary 

 fossils; as well as many Cretaceous forms, from the upper beds of that series 

 at Sage Creek, beneath the Tertiary: also, from a lower position at the Great 

 Bend, and from some of the still older beds farther down the Missouri. 

 While descending the Missouri from Fort Pierre to Bellevue, a trading-post, 

 not far above the present site of Omaha, especial attention was given to the 

 lithological characters, order of succession, characteristic fossils, etc., of the 

 subdivision of the Cretaceous series, and full notes taken in relation to 

 the same. The new Cretaceous fossils brought back by this expedition were 

 published, with figures by Professor Hall and the writer, in the Memoirs 

 of the American Academy of Arts and Sciences, at Boston, vol. v, in 1856. 

 The following section of the Cretaceous rocks, made out from the notes 

 of the writer, was also given in this paper, on page 405 of the same volume; 

 the thickness of the various beds being merely given from estimates made 

 of the exposures -seen along the Missouri, and back along the line of travel 

 from Fort Pierre to the Bad Lands: 



* Report of the Geological Survey of Wisconsin, Iowa, and Minnesota, and incidentally of a 

 portion of Nebraska Territory, njado under instructions from the United States Treasury Department; by 

 David Dale Owen. Philad., 1852. 



