The foregoing Report was written, for the most part, over three years since, and contains a condensed state¬ 
ment of the geological information concerning the Upper Missouri which had been secured up to that time. It 
may be regarded as a report of progress, and will be followed by the more complete and more matured results of 
the Expedition of 1859 and *60, under Capt. Wm. E. Raynolds, which are now in an advanced stage of preparation. 
The cost of publication has rendered it necessary to omit the illustrative sections, and many other details, which 
would have added materially to the value of the work. 
A detailed account of the geology of the White River group, Loup River beds, and the Judith River depo¬ 
sits, has been omitted, on account of the intention of the author to visit those localities again at no distant day, 
and to make a thorough exploration of them. 
The Map accompanying the*memoir is reduced from the military map of Nebraska and Dakota, by Lieut. G. 
K. Warren, T. E. Many of the details of the topography have been omitted. 
It remains now for the author to acknowledge his indebtedness to several gentlemen who have aided him 
during the progress of the Report. To Lieut. G. K. Warren, under whose direction, as commander of the Expe¬ 
ditions, the greater portion of the information was obtained, the writer is indebted for every facility and assistance 
that could be afforded, consistent with the public service. The memoir itself bears ample evidence of the kind 
aid and counsel, ever freely given, by my friend and associate, Mr. E. B. Meek. Messrs. Baird, Cope, Gill, Lea, 
and Binney revised the Catalogues in their respective departments. Dr. Engelmann and Prof. Dewey prepared 
the Catalogue of Plants. Dr. J. Sw Newberry furnished some valuable information for the Map in regard to 
Southern Kansas. 
To the Smithsonian Institution, and to its distinguished Secretary, Prof. Henry, the writer, during all his 
investigations in regard to the geology and natural history of the Upper Missouri, is indebted for the use of 
rooms, books, and every facility essential to the successful prosecution of his labors. 
ERRATA. 
Page 14, last line of second paragraph, for “ Meycochcerus 1 ' 1 read, “ Merychochcents .” 
Page 16, fourth line from bottom, for “La Pule” read “ La Prele.” 
Page 18, fifth line from top, for “above” read “preceding.” 
Page 36, sixth line from top, for “ Juya-kara Peak” read “Inya-kara Peak.” 
Page 68, second line from bottom, for “will” read “shall.” 
Page 69, for “ Ammonites alpinianus” read 11 Ammonites Galpinianus .” 
Page 94, for “ Corbula matriformis ” read “ Corbula mactriformis .” 
Page 116 v first line of second paragraph, for “appears” read “appear.” 
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