SURVEY OF COLORADO AND NEW MEXICO. 91 



age. The layers are nearly horizontal, and, as shown in the valley of 

 Green River, preseut a peculiarly handed appearance. When carefully 

 studied these shales will form one of the most interesting groups in the 

 West. The flora is already vei'y extensive, and the fauna consists of 

 3£elanias, Corhulas, and vast quanties of fresh-Avater fishes, preserved in 

 much the same way as those in the Soleuhofen slates of Germany. 

 There are also numerous insects and other small undetermined fossils 

 in the asphaltic slates. One of the marked features of this group is 

 the great amount of combustible or petroleum shales, some portions of 

 which burn with great readiness, and have been used for fuel in stoves. 



The next group commences not far w^est of Bryan, and is doubtless a 

 prolongation upward of the Green Eiver shales, and may be regarded 

 as of upper teitiju:y age. 



The sediments are composed of more or less fine sands and sandstones, 

 mostly indurated, sometimes forming compact beds, bnt usually weath- 

 ering into those castellated and dome-like forms which have given such 

 celebrity to the " Bad Lands" of White Eiver. Church Buttes, near 

 Fort Bridger, is an example of this groui), and shows the style of 

 weathering to which I refer. I have called this series of beds the 

 Bridger_grQHP, from the fact that it is best developed in this region. It 

 haslilready yielded remarkably fine species of JJnio, Mekmia, Flanorbis, 

 Vivipara, Helix, &c., with a great variety of turtles and mammalian re- 

 mains. There are indications that when this group is thoroughly ex- 

 plored it will prove to be second only to the " Bad Lands " of Dakota in 

 the richness and extent of the vertebrate remains. 



Immediately west of Fort Bridger commences one of the most re- 

 markable and extensive groups of tertiary beds seen in the West. They 

 are wonderfillly variegated, some shade of red predominating. This 

 group, to which I have given the name of Wasatch group, is composed 

 of variegated sands and clays. Very little calcareous matter is found 

 in these beds. 



In Echo and Weber Caiions are wonderful displays of conglomerates, 

 fifteen hundred to two thousand feet in thickness. Although this group 

 occupies a vast area, and attains a thickness of three to five thousand 

 feet, yet I have never known any remains of animals to be found in it. 

 I regard it, however, as of middle tertiary age. 



After passing Rock Springs station, Union Pacific railroad, the next 

 exposures of coal are at Bear River City, and at E^'anston, and also at 

 Coalville, near the entrance of Echo Creek into Weber River. The coal 

 beds at Evanston are the finest known in the West, and reach a thick- 

 ness of twenty-six feet at one locality. These coal beds seem to be sep- 

 arated from those at Separation and Carbon, and to present some feat- 

 ures different; from those in any other j^ortion of the West. I am in 

 doubt as to their precise position, but I am inclined to regard them as 

 of lower tertiary age, possibly on a parallel with the oldest beds of the 

 great ligiiite group in other localities. On Bear River we find several 

 species of Ostrea, both above and below the coal, and in a cut just west 

 of Bear River City is found the greatest profusion of molluscous life 

 that I have ever seen in any of the tertiary beds of the AVest. There 

 seems here to be a mingling of fresh and brackish water fossils. At 

 Evanston, impressions of deciduous leaves are abundant in beds above 

 the coal. ISTo portion of the fauna seems to be identical with anything 

 found in other x>laces. The flora seems also to be distinct, although 

 some of the forms may be identical with species elsewhere. I have 

 named the group of coal strata which is exposed from beneath the mid- 



