24 INTRODUCTORY REMARKS. 



The mammalian remains of the Mauvaises Terres were first brought to notice through communi- 

 cations of Dr. Hiram A. Prout, of St. Louis, published in the American Journal of Science for 1846, p. 

 288, and for 1847, p. 248, giving an account of a portion of the lower jaw of a large animal, supposed 

 to be a Paheotherium. 



Nearly at the same time, a few specimens, collected by persons mostly connected with the American 

 Fur Company, and sent to their friends as curiosities, were submitted to the author for examination, 

 and form the subjects of short communications in the Proceedings of our Academy for 1847. Some of 

 these specimens were afterwards presented to the Academy, and now form part of our museum. 



In 1849 Dr. David Dale Owen, while engaged in a geological survey of Wisconsin, Iowa and 

 Minnesota, extended his explorations into the then territory of Nebraska. One of his assistants. Dr. 

 John Evans, visited the Mauvaises Terres, and made a collection of vertebrate fossils, which form the 

 material of a contribution of the author to Dr. Owen's Geological Report, published in 1852. 



In 1850 Mr. T. A. Culbertson, under the auspices of the Smithsonian lustitution, visited the Upper 

 Missouri region, and during the expedition obtained a collection of the Mauvaises Terres fossils. This 

 material, together with that previously obtained, form the basis of a work of the author published in 

 1852, in the Smithsonian Contributions, under the title of " The Ancient Fauna of Nebraska." 



In 1853 Dr. John Evans again visited the Mauvaises Terres incidentally, on his way overland to 

 Oregon, for the purpose of making a geological survey of this territory. He made a large collection of 

 mammalian fossils and remains of turtles, and sent it to the Smithsonian lustitution, from whence it 

 was trausmited to the author for investigation. At the same time Dr. F. V. Haydeu and Mr. F. B. 

 Meek were employed by Professor James Hall to visit the Mauvaises Terres of White River, for the 

 purpose of making a collection of fossils. The collection of vertebrate remains, in extent and number 

 of peculiar species, almost equalled that of Dr. Evans, and this was likewise submitted to my examina- 

 tion, with the utmost liberality, by Prof. Hall. 



Subsequent to all these expeditions. Dr. Hayden in 1855 again visited the territory of Nebraska, and 

 spent the greater part of two years in exploring its geology. A large collection of fossils obtained by 

 him in the Mauvaises Terres was equally divided, one part being jjurchased by the Academy of 

 Sciences of St. Louis, the other part by this Academy. 



Both divisions of the latter collection, together with all the collections and specimens previously 

 indicated, constituted the material of a report on the tertiary vertebrate fauna of the Mauvaises Terres, 

 accompanied with drawings, which was submitted by the author to Dr. Johu Evans, to be published 

 with his Report on the Geology of Oregon and Washington Territories, prepared for the United States 

 Government. 



Dr. Evans died in 1861, while engaged in preparing his work for the press. Learning that Dr. 

 Evans' Report was left in a very incomplete state, the author during several years made repeated 

 attempts to procure his own contribution to the work from the proper authorities at Washington, with 

 the view of publishing it through another source. The efforts to obtain the manuscript and drawings 

 having proved unsuccessful, and there being no reasonable prospect that they could be procured by 

 renewed trial, the author concluded that he once more would ^o through the labor of preparing the 

 work for the press. 



In 1857 Dr. Hayden accompanied Lieut. G. K. War-en, then of the U. S. Topographical Engineers, 

 on an expedition to the country of the Upper Missouri. During this expedition he made the highly 

 important discovery of a formation on the Niobrara River, iu the present State of Nebraska, certainly 

 newer thau that of the IMauvaiscs Terres, of White River, Dakota, and supposed to be of pliocene age. 

 Tlic formation was rich in remains of mammals and a species of turtle, of which Dr. Hayden obtained 

 a large collection, including mauy species evidently exhibiting a relationship on the one hand with tlie 



