1875.] 4:7d [Stevenson. 



membered, that at no great distance from the mountains, this group is 

 no longer within reach, having been removed by erosion, or buried under 

 later deposits. Let us look at the succession of the whole series, Cre- 

 taceous and Lignitic, in New Mexico and Colorado : 



New Mexico. Colorado. 



1. Bright-yellow to red and gray 1 . Same as in New Mexico, 



sandstones, more or less con^ 

 glomerate and concretionary, 

 with lignites, containing 



many mollusks, and ifaZ^/"^^'^- 



ites major throughout. 

 3. Shales, limestones, variegated 2. Same as in New Mexice. 



marls, some of the shales 



sandy. 

 3. Bright-yellow to gray sandstones 3. Same as in New Mexico. 



with shales and lignites. 



No. 2 is the Middle Cretaceous representing Nos. 2, 3, and 4 of the 

 Upper Missouri Group, while No. 1 represents the Lignitic Group and 

 Cretaceous No. 5. There is no difficulty in proving the identity of the 

 two sections ; it is simply a matter of tracing. In the New Mexico 

 region. Dr. Newberry found at occasional exposures many characteristic 

 Cretaceous species, while in its uppermost layers, Prof. Cope found a 

 rich profusion of specimens. 



East from the mountains, at rare localities. Dr. Leconte, in Colorado, 

 and Dr. Hayden, further north, have found Cretaceous species in the 

 lower portions, while in the topmost portions Mr. Arnold Hague and 

 myself have found a grand profusion of species characteristic of Creta- 

 ceous No. 5. Far in the interior, Messrs. Meek and Bannister have 

 found the undoubted Cretaceous forms at various horizons in the series. 



Sixthly, That there is an u.tter lack of any positive evidence to show 

 that the series is of later date than the Cretaceous. This statement may 

 seem strange in view of Mr. Lesquereux's very emphatic assertion that 

 the flora proves Tertiary age beyond all doubt. 



The reasons given in a previous portion of this paper, are certainly 

 sufficient to show that, in our present stage of knowledge, the testi- 

 mony of plants can have no bearing upon the discussion. If a witness 

 be shown utterly unworthy of credence in an important case, he cer- 

 tainly cannot be received as trustworthy in a similar and equally impoi't- 

 ant case. Falsus in uno, falsus in omnibus. "We have seen already that 

 the plants showed the Dakota Group to be Miocene, and the Vancouver 

 Coals to be of the same age. Yet everybody concedes that their testi- 

 mony was invalid in the former instance, and everybody, excepting Mr. 

 Lesquereux, concedes the same in the latter case. 



But Mr. Lesquereux points out that the flora of the Great Lignitic 

 Group is very diff'erent from that of the Dakota Group. This is not won- 



