LETTER OF TRANSMISSION. 



January 1, 1879. 



Sir : I send herewith a report on the Tertiary Faunae of the United 

 States as represented by collections made in various Territories and States 

 west of the Mississippi River, embraced within the boundaries of your sur- 

 vey. The explorations from which the collections have been derived cover 

 portions of the States and Territories included between British America on 

 the north, the western boundaries of Minnesota and Missouri on the east; 

 the northern borders of the Indian Territory and Arizona, and the middle 

 of New Mexico on the south; and the Sierra Nevada on the west. The 

 amount of material which I have procured through these explorations is 

 large, and is but partially represented in the following pages. I trust that 

 you will find the results a useful contribution to the records of your Geo- 

 logical Survey and to the science to which you have devoted your life ; and 

 that you may find in this report some compensation for the arduous official 

 duties which have recently withdrawn you to some degree from your chosen 

 field of research. 



The preface gives an account of the methods pursued in conducting 

 the investigation ; while the introduction embraces a general view of the 

 stratigraphy of the Tertiary formations of the West. The system adopted 

 is that proposed by yourself and Mr. King, with a few additions ; while 

 several correlations with the horizons of the Old World are based on my 

 own paleontological studies. The order of succession of faunae is observed 

 in the following sections of the work; that is, part first, the Puerco, Wasatch, 

 and Bridger formations ; part second, the White River and the John Day 

 beds ; and part third, the Loup fork and Equus beds. The second half of 

 the second part, the third part, and faunal lists, will constitute the succeed- 

 ing volume. No. IV, of your series. 



I desire to express here the obligations under which I have been placed 



