Albany, N. Y., December 10, 1876. 

 Dear Sir: 1 herewith submit to you the following- rei)ort on the fos- 

 sils collected by the United States Geological and Geographical Explora- 

 tions in the Black Hills of Dakota during the summer of 1875, and placed 

 in my hands for determination. 



The report contains figures and descriptions of the fossils of the Pri- 

 mordial, Jurassic, and Cretaceous formations only, those of the Carbon- 

 iferous not being deemed of sufficient interest to warrant the expense. 



I have been under obligations to the officers of the Smithsonian Insti- 

 tution for the oppoitunity of making comparisons with their collections from 

 the same formations, and to Dr. C. A. White for personal courtesies while 

 so doing. I have also availed myself of the ver}- valuable work of F. B. 

 Meek, esq., on the fossils of that region, lately published by the Department 

 of the Interior, a copy of which was sent to me at his request at the earliest 

 moment it could be obtained. 



Very respectfully, yours, &c., 



R. P. WHITFIELD. 

 W. P. Jenney, E. M., 



In charge Exxiloration of the Black Hills. 



3S7 



