Stevenson.] 4:0^' [June 18, 



from light-red to deep brick-red, dull-purplish, deep-yellow, white, 

 brown, drab, etc. The only fossils are silicified trunks of trees. 



3. Santa Fe Marls, which rests unconformably upon the Galisteo Group, 

 and are of much later date. 



Dr. Hayden of course refers this whole section to the Tertiary. Mr. 

 Lesquereux does the same, in consideration of six species of leaves, four 

 of which are peculiar to the locality, and two occur elsewhere, also. But 

 a careful comparison of this section as given by Dr. Hayden, with the 

 details of the geology along Dr. Newberry's route from Santa Fe west- 

 ward, as given in Ives' report, will, I think, satisfy anybody that Dr. 

 Hayden has by some oversight inverted the order, and that the Galisteo 

 Group underlies the Coal Group. The Galisteo Group is unquestionably 

 the Triassic, as abundantly appears from the descriptions of that system 

 in New Mexico, by Newberry and Leconte. 



In Utah and New Mexico, Messrs. Gilbert and Howell have found coal 

 beds of much economical value at about the horizon of this group, but 

 their work, being unpublished, is not accessible. 



The Uppek or Great Lignitic Group. 



This is the Fort Union Group of Dr. Hayden. Its relations to the 

 Upper Cretaceous are so intimate that the description of the one requires 

 constant reference to the other. 



This group, so far as our present knowledge extends, seems to pass but 

 little beyond our northern boundary. For information respecting its 

 character at the north, I have consulted the writings of Messrs. Hayden, 

 Meek, Lesquereux, and Emmons, while for the southern extension in 

 Colorado and New Mexico, I have drawn from the observations of Hay- 

 den, Lesquereux, Leconte, Cope, and myself. 



Dr. Hector observed some lignites at La Roche Percde, not far north 

 from the United States boundary line, which he regards as the northern 

 extension of the Missouri lignite basin, and therefore places them in the 

 Tertiary, though he thinks they may possibly be Cretaceous. Prof. Hind 

 thinks that they belong to the Fox Hills Group of Meek and Hayden. 



Throughout the JJ'p'per Ilissouri Eegion, this Lignite Group is perfect- 

 ly conformable to the Upper Cretaceous, and the line of separation can- 

 not be determined. During many years of exploration, only one case of 

 unconformability, that between Spring Canon and Bridger Peak on 

 Laramie Plains, has been found. 



On the Yellowstone, below the mouth of Big Horn River, the Upper 

 Cretaceous (5) passes upward into a dark-gray sandstone, containing many 

 Cretaceous species. This, in turn, changes into a coarse-grained friable 

 ferruginous sandstone, containing many concretions. This latter rock 

 yielded a few indistinct bivalves, which were evidently of marine origin. 

 At a locality between Big Horn and Powder Rivers, No. 5 is composed of 

 clay and marls, with layers of concretionary, ferruginous, calcareous sand- 

 stone, containing several Cretaceous species. It passes almost imper- 



