LETTER TO THE SEORETAEY. 



Sir : I have the honor to present for your approval and for publication the 

 first part of volume I of the quarto series of reports which are intended to 

 embody the more original and technical results of the survey under my direc- 

 tion. The present memoir on the " Extinct vertebrata of our Western Terri- 

 tories" has been elaborated by Professor Joseph Leidy, the eminent compar- 

 ative anatomist, and will form one of -the most important contributions to the 

 science of extinct organisms ever made in this country. This memoir will 

 be followed by a second part on the same subject by Professor E. D. Cope. 



Volume II will embrace the subject of the extinct flora of our western 

 Territories ; and it is the purpose to make it as exhaustive as possible. Pro- 

 fessor J. S. Newberry is preparing the first part and Professor Leo Lesque- 

 reux the second. The well-known reputation of these gentlemen is a suffi- 

 cient guarantee for the value of their work. 



Volume III will include all the materials collected by the survey on the 

 subject of extinct invertebrata, and will be most carefully elaborated by the 

 eminent paleontologist of the survey, Mr. F. B. Meek. 



Volume IV will embrace the profiles, sections, maps, and other illustrations, 

 with descriptive text by the geologist in charge. 



Volume V will contain separate memoirs on different subjects in recent 

 zoology and botany, prepared by several authors. All the new and imper- 

 fectly described species of plants or animals collected by the survey will be 

 studied and fully illustrated. All these volumes are now in an advanced state 

 of preparation. In presenting to the world these important contributions to 

 science, permit me, sir, to extend to you my sincere thanks for your intelli- 

 gent sympathy and hearty co-operation in the work. 

 Very respectfully, your obedient servant, 



F. V. IIAYDEN, 

 United States Geologist. 



Hon. C. Delano, Secretary of the Interior. 



