376 THE JOURNAL OF GEOLOGY. 



Large numbers of huge vertebrate remains, only known from 

 " The Laramie of Wyoming," fortunately have fragments of 

 fossil plants adhering to them, from the study of which impor- 

 tant light will be thrown on the age of the beds in which they are 

 contained. 



Along the Missouri river in the vicinity of Great Falls, Mon- 

 tana, there is exposed a considerable thickness of mainly brown, 

 sandstone rocks. They have been eroded by the river into more 

 or less of a canon, and are the material in which the falls have 

 been developed. From their lithologic appearance, but mainly 

 upon stratigraphic grounds, these rocks have been referred by 

 geologists to the Dakota group. On going down the river they 

 disappear under the Fort Benton shales, and are consequently in 

 the stratigraphic position of the Dakota, but the recent discovery 

 of plant-beds near Great Falls has shown the impossibility of 

 such reference. The plants are typically lower Cretaceous, and 

 have been positively identified by Newberry with the Kootanie 

 of Canada. By this a part at least of the so-called Dakota goes 

 to the lowest Cretaceous. 



In a similar way a part of the supposed Dakota of the Black 

 Hills has been shown by Professor Ward,^ purely on paleo- 

 botanical evidence, to belong to the lower Cretaceous. 



The Foreman beds in the Taylorville region, Plumas county, 

 California, were determined to be of Rhgetic age from the fossil 

 plants, a determination agreeing perfectly with the stratigraphy.^ 



The copper mines near Abiquiu, New Mexico, were identi- 

 fied as Triassic by the plants found in and about the roof of the 

 openings. 3 



The employment of fossil plants in practical mining exploita- 

 tion is well shown by the results obtained by Grand' Eury and 

 Zeiller in Southern France. 



In the Department of Gard the mining of coal is one of 



'Journal of Geology, Vol. II., No. 3, pp. 250-266. 



^DiLLER : Bull. Geol. Soc. Am., Vol. 3, p. 373. 



3 Fontaine & Knowlton : Proc. U. S. Nat. Mus., Vol. XIII., 1890, p. 282-285. 

 Newberry: Rep. Expl. Ex. in 1859 under Macomb. Wash., 1876, p. 140. 



