F. H, Knowlton — Tertiary Floras^ etc. 51 



Art. YII. — The Tertiary Floras of the Yellowstone 

 National Pcirk ; by F. H. Knowlton, of the U. 8. Geologi- 

 cal Survey. 



It has long been known that the Yellowstone National Park, 

 in addition to its numerous interesting geological features, 

 possesses what is probably the most remarkable fossil forest 

 known, and an abundance of finely preserved fossil plants. 

 The writer has been engaged, for the past year or more, in the 

 careful study of this flora, and the present paper has been 

 prepared for the purpose of calling attention to some of the 

 more important geological and biological results. The full re- 

 port, with descriptions of new species and illustrated by forty- 

 five quarto-plates, will appear in a monograph of the U. S. 

 Geological Survey. 



The localities that have supplied the Tertiary flora are all 

 located in the north-eastern part of the Park, in the vicinity of 

 the junction of the Lamar Piver with the Yellowstone, and 

 along the Lamar Piver for a distance of ten or twelve miles from 

 its mouth. The flrst fossil plants obtained from that portion of 

 the Park were brought back by the early Hayden Survey 

 parties. They were submitted to Prof. Leo Lesquereux, and 

 although few in number, the species were nevertheless suffi- 

 cient to afford some indication of their age. Professor 

 Lesquereux regarded the plants from Elk Creek and vicinity 

 as indicating an Eocene age, and those from the well-known 

 Fossil Forest on the west side of the Lamar Yalley as closely 

 allied to the Auriferous Gravels of California. It is a pleasure 

 to state that this adumbration has been abundantly confirmed 

 by the results of more searching study of a larger amount of 

 material; but at the time Lesquereux's statement w^as made, the. 

 facts were so few that the suggestions were not regarded as 

 conclusive, and as it was before careful, detailed geological 

 work had been done, these now clearly-defined beds came 

 to be grouped together under the somewhat non-committal 

 term Yolcanic Tertiary. 



Although the geology of the region has been fully discussed 

 by Mr. Arnold Hague in a preceding article,* it seems 

 necessary for a satisfactory understanding of the problems re- 

 quiring solution to set forth briefly the geological features 

 characterizing this portion of the Park which have a direct 

 bearing upon the remarkable flora found. In the first place, 

 all the material constituting the beds, in which the Tertiary 

 plants are imbedded, is of volcanic origin. According to the 

 geologists, this material may be divided into two distinct 

 periods of volcanic eruption which can be distinguished by 

 their mineral composition. 



* June number, p. 445. ' 



