182 Cincinnati Society of JSfatiiral Hisforif. 



Fox Hills Group, and it is difficult to determine where one formation 

 ends and the next begins. From Dr. Peale's examination and stud}^ 

 he deduced the following conclusions: 



1. The lignite-bearing beds 'east of the mountains in Colorado 

 are the equivalent of the Fort Union Group of the Upper Missouri, 

 and are Eocene-Tertiar}- ; also that the lower part of the group, at 

 least at the locality 200 miles east of the mountains, is the equivalent 

 of a part of the lignitic strata of Wyoming. 



2. The Judith river beds have their equivalent along the eastern 

 edge of the mountains below the Lignitic or Fort Union Group, and 

 also in W3^oming, and are Cretaceous, although of a higher horizon 

 than the coal-bearing strata of Coalville and Bear river, Utah. They 

 form either the upper part of the Fox Hills Group, or a group to be 

 called No. 6. 



3. That the upper part of the Fox Hills Group is wanting in man}^ 

 parts of Eastern Colorado, and when present seems to be thin and 

 destitute of coal. 



F. M. Endlich surveyed the San Juan mining district, where he 

 found the Dakota Group restino- unconformabh^ upon carboniferous 

 sandstone. It consists of sandstones with occasional remains of 

 plants, and has an estimated thickness of SOO to 1,000 feet. The Fort 

 Benton Group, consisting of dark-gra}^ shales, subject to considerable 

 erosion from the action of water, is found from 400 to 600 feet in 

 thickness. It contains beds of coal. 



These groups are also developed on the San Miguel and on the Rio 

 Dolores. A creek flowing scarcely five miles has at the junction with 

 the San Miguel a canon 1,005 feet in depth. The entire canon is cut 

 out of the strata of the Dakota Group, and 3^et the whole thickness is 

 not exposed. 



Prof. Leo Lesquereux found the flora of Point of Rocks related to 

 that of Black Butte by nine identical forms or one-third of its known 

 species, notwithstanding that there are two to three thousand feet of 

 interposed measure;^ The distance between the two localities is onh' 

 eleven piles, and the superposition of the strata is exposed so that the 

 vertical thickness of the intervening rocks maj' be easily ascertained. 

 He explained the scarcity of the bones of animals in the lower beds of 

 the Lignitic, b}^ the fact that, no animal, not even man, if once im- 

 bedded in soft peat, can get out of it, and also b}^ the further fact 

 >fchat the coriaceous, ligneous plants of the bogs are not*" food for 

 mammals. ' 



He described, from the Lignitic at Point of Rocks, Fiicus lignitum, 



