Douglass : Geology of Southwestern Montana. 427 



the Jurassic is very well ex])osed. Here, as stated before, it lies upon 

 the Carboniferous. In one place on the eastern slope just below the 

 crest of the range a little stream issuing from a spring in a swampy 

 place has washed out bones of large Dinosaurs. Those exposed are 

 water- worn. In the sandstones I found some poor invertebrate fossils. 



LOWER CRETACEOUS? 



Near Drummond in Granite County, in a comi)act greenish-brown 

 rock, I found some fossil ferns resembling Fecoptcris and leaves that 

 look like SferciiUa, which are i)robably lower Cretaceous, but they 

 have not been determined and nothing definite can be said concern- 

 ing the age. They may prove to be Kootenai. 



DAKOTA. 



In the various Montana Atlas folios and geological maps of Mon- 

 tana, strata have been mapped as doubtfully Dakota on the evidence 

 of the position of the beds but in none of them had characteristic 

 fossils been found. For the most part the formation mapped as 

 Dakota contains a heavy band of limestone which is very fossilifer- 

 ous, containing, wherever exposed, great numbers of bivalves and 

 gasteropods. 



In the Jack Creek (Jackass on the map) Canon in the strata mapped 

 as Dakota on the Three Forks Atlas Sheet, I collected fossil leaves. 

 Part of these are in the LJniversity of Montana and the remainder in 

 the Carnegie Museum. The latter were sent to Professor F. H. 

 Knowlton, who determined the following : 

 Sequoia I'eichenbachi ? 

 Qiiercus primordialis. 

 La urns protCBfoIia. 

 Ficus lanceolata acuminata. 



These are all Dakota species. The leaves came from layers of sand- 

 stone in sandy clay. Above, but, according to A. C. Peale lower 

 geologically, is a considerable thickness of gray sandstone. This is 

 probably the horizon which Peale says contains fragments of fossil 

 leaves.^ The lithological character of the rocks here is nothing like 

 that of the beds which contain so many gasteropods, etc., in other 

 places. 



^ Si.xth Ann. Report, U. S. Geol. Surv. of Terr., p. 163. 



