CHAPTER VIII. 
AGE OF THE LIGNITE-BEARING FORMATION AND POSITION OF THE 
3. LINE SEPARATING THE CRETACEOUS AND TERTIARY. 

AGE oF THE LIGNITE FORMATION—Nature of the question—Physical break between 
4%. Cretaceous and Tertiary of Europe—No physical break in Interior Conti- 
hers nental region — Unity of the Lignite formation — Tertiary age of Eastern 
“fora representatives not directly questioned—Summary of facts and opinions bear- 
ing on the age of Lignite formation—Stratigraphical—Invertebrate fossils— 
Fossil plants—Vertebrate remains—Character of Junction Cretaceous No. 5 
and Lignite formation—-Contemporaneous deposit of No. 5 over the entire 
area.—REVIEW OF THE EVIDENCE—Plants—Fresh-water molluscs—Marine 
molluses—Vertebrates—General conclusions. 

432. In adopting the name Lignite Tertiary, as that of the great 
newer coal-bearing formation of the west, and using it—as has been 
done throughout—to designate the part of the series which lies above the 
<— : ; 
____ 5th or Fox Hill group of Meek and Hayden’s Cretaceous section, I have 
a not done so carelessly, but as the result of a careful, and I hope impartial, 
i. review of all the evidence bearing on the age of the formation, to which 
[have access; as well as the study of the rocks in the vicinity of the 
: a. forty-ninth parallel, which have come under my more immediate atten- 
tion, and which seem to throw important light on the question. It would 
appear only proper to state the reasons which have had most weight in 
leading to the formation of this conclusion, and this will now be done as 
briefly as possible. The subject is a delicate one, insomuch as it has 
been the topic of much eager controversy, but it is hoped that injustice 











that if errors have crept in unobserved, good intentions will serve as an 
apology. Nor can the gradual change of opinion—now a matter of 
geological history—which has taken place on some points with the 
advance of knowledge with regard to the beds, be considered derogatory, 
_____ for nothing can be more honorable or truly scientific than that impar- 
— dency, the prompt retractation or modification of views formerly 
upheld. 
433. There is, perhaps, no more interesting problem in. American 
geology, than that presented by the later deposits of the interior region 
has not been done to the views of any of the gentlemen concerned, and. 
tiality which allows, on the knowledge of new facts of a different ten- . 

