LIGiNITIC FORMATION AND FOSSIL FLORA. 



BY LEO. LESQUEREUX. 



Columbus, Ohio, March 25, 1873. 



Dear Sir : Accordiug to the directions received from you, I spent 

 the months of July and August in exploring, first, the plant-bearing 

 Cretaceous strata of the Dakota Group, in the valley of tbe Saline Eiver 

 and on the Smoky Hill Fork of the Kansas ; then the Lignitic foimation 

 of the Eocky Mountains, from Trinidad to Cheyenne, and along the 

 Union Pacific Eailroad to Evanstou. You requested me to have these 

 explorations especially directed in view of positively ascertaining the 

 age of the Lignitic formations, either from data obtainable in collecting 

 and examining fossil vegetable remains, or from any'geological observa- 

 tions which I should be able to make. 



The following report gives the details of these researches. Its divis, 

 ions are marked by the nature of your instructions. The first \)iiit- 

 after recording the facts derived from explorations at different localities, 

 discuss the age of the Lignitic in considering geological and paleonto- 

 logical evidence. The second part reviews what is as yet known on the 

 formation of the lignite, the distribution of the lignitic basins, their pro- 

 ductive capacity for combustible mineral, and the present application 

 of the material. The third part enumerates tli^ species of fossil-plants 

 obtained in the explorations of this year, either by myself or other of 

 your assistants, describes the new species, and comi^ares their local 

 distribution, &c. 



On this last point my researches have been very successful. I ob- 

 tained, from the Cretaceous and from the Lignitic, a large number of 

 good specimens, which, selected in place and there compared, allowed 

 me to fix more positively the characters of many species either not sat- 

 isfactorily known or as yet undescribed. This work was rendered es- 

 pecially profitable by the assistance of Mr. L. Lesquereux, jr., who 

 pursued the researches with scientific interest and unceasing energy, 

 and who frequently discovered at remote or distant places the richest 

 deposits of fossil vegetables. 



Allow me, sir, to gratefully acknowledge the valuable assistance re- 

 ceived from yourself in railroad passes, letters of introduction, &c., 

 still more by information from your former reports, and also to men- 

 tion the kind assistance offered everywhere to my explorations by the 

 superintendents of mines, the engineers of railroads, the proprietors, 

 &c., who generallj' manifested interest in my researches. At Fort Bar- 

 ker and Medicine Bow a generous hospitality was offered me by Lieu- 

 tenant Edward Eandall and Lieutenant Hall, commanding the stations. 

 I am also indebted to Messrs. B. C. Smith and Eugene Ford for i)asses to 

 Saint Louis, also to E. A. Ford for pass to Kansas City, and to Colonel 

 Fisher for pass from Denver to Cheyenne. 

 Very respectfully, yours, 



L. LESQUEEEUX. 



Professor F. V. Hayden, 



United States Geologist, Washingtov. J). C 



