332 GEOLOGICAL SUKVEY OF THE TERRITORIES. 



perliaps the presence of the Lignitic at that locality. These rocks,~^a kind 

 of silieeoLiSj reddish-brown sandstone, hardened by metamorphism, are 

 exposed in a thickness of 200 to 300 feet in bluffs on both sides of the 

 railroad, half a mile west of the station. They overlie the upturned 

 edges of granitic rocks, which come to the surface one mile farther north, 

 and, indeed, they contain an immense abundance and variety of fucoids, 

 without any traces of animal remains. I have never seen plants of this 

 kind filling rocks in such quantity, except in some ferruginous shale of 

 the Devonian of Ohio, or in some groups of the Silurian of New York 

 and Pennsylvania, the Trenton and the Clinton groups. 



These marine plants belong to types far different from those of the 

 fucoids of the Tertiary. This is immediately recognized, especially in 

 their large size, as remarkable as the quantity of their remains. Some 

 branches or trunks measure more than half a foot in diameter, while 

 their ramifications, filling the rocks and crossing the layers in every di- 

 rection, cover large surfaces by a confused mass of filaments. They look 

 like heaps of sea-weed crushed, flattened, and petrified at the same 

 time. The large-sized trunks of these plants are generally found near 

 the base of the formation, or in close proximity to the granite rocks, 

 ■while at a higher level the shales are mostly covered with small spe- 

 cies, perhaps mere branches of the large ones. Some of these, as far 

 as they can be recognized, are referable to Chondrites antiquus, Sternb ; 

 Buthotrephis succulosus and B. Jfexuosus, Hall, all species of the Silurian. 

 But, as said above, they are mixed in such a way that the ascertaining 

 of their specific characters would demand much time for a careful 

 study, which can be made only in place, small broken specimens being 

 useless for that purpose. But if even I had been able to determine 

 specifically a number of these plants, our acquaintance with the fucoids 

 of the old formations is as yet too limited to afford reliable points of 

 comparison, and therefore it would not be possible to refer those of 

 Rawlings to a peculiar division of the Silurian. That they'belong to the 

 Silurian epoch is all that can be ascertained, and thus the opinion of 

 Dr. Hayden on the age of these fucoidal rocks is corroborated by 

 l^aleontological evidence. 



The Same kind of fucoidal remains are seen also, but far less abun- 

 dant, in the red rocks overlying the primitive formations in Colorado ; 

 as, for example, in passing up Glen Eyrie from what is called the Gar- 

 den of the Gods. These plants may be remarked in the fragments 

 strewn along the borders of the run. The formation is evidently older 

 than that of the upturned red rocks which form the inclosure and the 

 monuments of the garflen. In these I did not find any fossil remains of 

 any kind at this locality ; but near Caiion City, from the upturned 

 ridge of red and white sandstone from under which the soda- springs 

 gurgle out, and which, from their position, are referable to the same 

 formation, I obtained a few fruits of the genus Trigonocarpum. With 

 some rare fragments of Calamites, recognized too in these rocks, they 

 would indicate their age as true Carboniferous or Lower Permian. In 

 crossing this ridge along Oil Creek, east of Canon City, the underlying 

 strata from which the bitumen there percolates, mixed with the water, 

 are mostly beds of black shale, which appear referable to the Devonian, 

 at least from the analogy of their comijound and color. I do not know 

 that any kind of fossil has been remarked in connection withthem, and 

 this, too, is a point of analogy with our oil-bearing Devonian black 

 shales, so esftensively developed from Arkansas to Pennsylvania, and rec- 

 ognized everywhere by their geological position and the large proper- 



