Stevenson.] 4:<(J [June 18, 



they are generally inclined to admit that the highest portions may be 

 Eocene. 



After a carefal study of plants collected by Dr. Hayden in the Upper 

 Missouri Region, Dr. Newberry referred the Fort Union Group, as there 

 exhibited, to the Miocene. This conclusion was based upon the close re- 

 semblance of this flora to the so-called Miocene flora of Greenland and its 

 intimate relation to the Miocene flora of Europe. Dr. Newberry still 

 holds this opinion respecting the Upper Missouri Region, though he shows 

 some inclination to dispute the assertion, that the southern portion is as 

 recent as the Eocene. The stratigraphical evidence, however, is so strong 

 to pi'ove the identity of the group throughout the Rocky Mountain Re- 

 gion, that all parts of the area must belong to the same horizon. If one 

 part is Miocene the other is Miocene also. 



Mr. Lesquereux has published several elaborate and very able papers 

 upon the flora of this group. Though it has close affinity to the Miocene 

 flora of Eui'ope, he does not regard it as Miocene throughout, but divides 

 the series containing it into Upper and Lower Eocene, the former repre- 

 sented at Garbon, Evanston, and 8age Greek, and the latter at Raton 

 Mountains, Golden, Black Butte, Spring Ganon, and Fort Union. As a 

 whole, he regards this vegetation as Oligocene. Above the Lignitic 

 Group he finds the Miocene at Oreen Biver, Elko Station, South and Mid- 

 dle Parks. 



Dr. Hayden has long halted between two opinions. He looks upon the 

 Coalville and Bear River sections as Cretaceous beyond doubt, but con- 

 cerning the rest of the Great Lignite Group he is by no means so de- 

 cided. Sometimes he speaks of the Lignite Tertiary, at others he seems 

 to regard the group as partly Cretaceous and partly Tertiary, while for 

 the most part in his more recent publications he is disposed to regard 

 the whole as, in great measure, beds of transition. From the beginning 

 his inclination has been to favor the Tertiary hypothesis. Under such 

 circumstances one cannot fail to admire the frankness with which all the 

 facts are given in Dr. Hayden's reports, many of them bearing directly 

 against the deductions previously published by the Doctor himself. Judg- 

 ing from his readiness to receive the truth even at the expense of discard- 

 ing cherished opinions, there is every reason to hope that before very long 

 Dr. Hayden will be one of the most energetic expounders of the doctrine 

 that the Lignitic Group is Cretaceous. 



Mr. Meek refers the Coalville and Bear River areas as well as a portion 

 of the Bitter Creek Series to the Cretaceous but thinks the upper portion 

 of the Bitter Ci'eek section may be Tertiary. He is quite positive that 

 the Black Butte portion of the section is Cretaceous ; but this lies far up 

 in the series. 



Prof. Cope is very positive resi^ecting the Cretaceous age of the Black 

 Butte section, because Agatliaumus sylvestris occurs there. Prof. Marsh 

 is equally positive regarding some other localities. Dr. Leconte, Mr. 

 Arnold Hague, and myself have referred the Colorado beds to the Cre- 

 taceous. 



