PLANT REMAINS FROM THE COAL-BEARING STRATA. 363 



slipping of the strata, and the coal is more broken than in the less disturbed 

 portions of the field. 



Age of the Coals. 



The stratigraphical evidence, which has been given in the preceding pages, 

 shows that the coal-bearing series is of later age than the marine Cretaceous, 

 and that it forms the base of the Laramie series. This conclusion is sup- 

 ported by the available paleontological evidence. 



Niobrara fossils have been found in the shaly belt of the section at Coke- 

 dale, but no positive identification of the Fox Hills sandstones could be 

 made. Uiiio shells were found associated with the coal seams of the Cinna- 

 bar field, and fossil leaves obtained from the shales between the middle and 

 upper seams have been placed in the hands of Professor Lester F. Ward. 

 Mr. F. H. Knowlton has examined a part of this material, and identified 

 Gymnogramma haydenii, Lx., and Ahietites dubius, Lx,, both very good 

 specimens, together with Salisburia {Gingko) polymorpha, Ung., and Gingko 

 adiantoides, Ung., from the beds overlying the coal seams, associated with 

 Platanus, Vitis, and a leaf of Ericacece. These are all lower Laramie types. 



A large collection of fossil leaves made by Dr. A. C. Peale from the rocks 

 overlying the coal seams of the Bozeman field, west of Timberline, at various 

 times from 1871 to 1888, and in recent years by Mr. Knowlton, have not as 

 yet been exhaustively studied by Professor Ward ; but after a brief exami- 

 nation he says that they closely resemble the collections from the coal strata 

 of Bitter Creek, Wyoming ; the following genera from these beds being 

 represented: Quereus, Viburnum, Betula, Vitis, Populus, Ficus, Gingko, Zizy- 

 phus, Sequoia. 



The earlier collections of Dr. Peale from these same beds were examined 

 by Professor Leo Lesquereux, and the list of species published in his Tertiary 

 Flora embraces the following : 



Abietites dubius, Lx. ; 

 Salisburia polymorpha, Ung. ; 

 (^uermis chlorophylla, Ung. ; 

 " ellisiana, Lx. ; 

 " pealii, Lx. ; 

 Dombeyopsis platanoides, Lx. 



Invertebrate fossils obtained by Dr. Peale from the sandstones beneath 

 the principal coal seams have been placed in the hands of Dr. C. A. White, 

 by whom specific determinations will be made. Dr. White has identified 

 Viviparus and Corbula for me from a sandstone four feet below the coal, and 

 tells me the shells found with the coal in the Cinnabar field are probably 

 Unio bridgerensis. These fossils prove the rocks to be brackish water de- 

 posits. 



