United Statk.s I^nginekk Office, 

 Geographical Explorations and Surveys 

 West of the One hundredth Meridian, 



Washmffton, D. C, December 15, 1875. 



General: I have the honoi' to submit herewith a report, in two parts, 

 upon the paleontological results arising from the collections and examina- 

 tions made during the years 1K71, 1872, 1873, 1874, and 1875, in connec- 

 tion with geographical explorations and surveys west of the one hundi-edth 

 meridian, for publication as Volume IV of the reports authoi'ized by Acts 

 of Congress approved June 23, 1874, and February 15, 1875. 



Part I is by Dr. C. A. White, on the collection of invertebrate fossils, 

 numbering one hundred and seventy-eight distinct species, of which fifty- 

 four are new to science. 



A preliminary report, with descriptions of new species, by the same 

 author, was, with your sanction, published in December, 1874, the sub- 

 stance of which is embodied in the present volume. 



The attainments and the experience of Dr. White in this branch of 

 science are a guarantee that his work has been well done. 



Part II is comprised of a similar treatment of the vertebrate fossil col- 

 lections, by Prof. E. D Cope, who has given to this subject years of study. 

 Professor Cope was connected with the expedition during the season of 

 1874, in which he made collections himself, and, in addition, was enabled to 

 prosecute geological researches. A portion of his results were published in 

 preliminary form in a "Report upon the Vertebrate Fossils discovered in 

 New Mexico, with description of new Species," November 28, 1874; and a 

 "Systematic Catalogue of the Vertebrata of the Eocene of New Mexico, 

 collected in 1874," April 17, 1875. tlis geological deductions appear in my 

 annual report. Appendix LL, Annual Report of the Chief of Engineers, 1875 



Several members of the expedition not engaged upon paleontological 



work have made collections of interesting specimens, evincing a hearty 



co-operation in this as well as other allied branches of the survey. 



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