The que 

 by Dr. Pes 



Qeohgy and Mineralogy. 497 



s to the age of the Lignitic beds is well discussed 

 d in the course of this discussion a full tabular 

 list IS given of all papers ou the subject hitherto published, their 

 places of publication, and the views they present, the several re- 

 gions of the beds being taken up in succession. 



The conclusions are: 



That the Lignitic beds of Coalville and Bear River are un- 

 doubtedly Cretaceous : whether the Evanston should be included 

 IS left doubtful. 



That the Judith beds are Cretaceous, and have their equivalent 

 along the eastern edge of the Mountains (Front Range) below 

 the Lignitic or Fort Union group, and also in Wyoming, and are, 

 either, part of No. 5 (Fox Hills Group) of the Cretaceous, or, a 

 group to be called No. 6. 



That the coal (which is partly anthracite) of Rock Creek, Slate 

 Creek, Anthracite Creek and Ohio Creek, is probably all of Cre- 

 taceous age. The coal of some beds is excellent, two analyses 

 giving 88-2 and 91-9 p. c. of carbon. The anthracitic character is 

 owing to a trachytic eruption. 



That the Fort Union group (at Fort Union, Fort Clark, and 

 under the White River beds, on the North fork of the Platte 

 River, above Fort Laramie and west of Wind R. Mts., also 

 on Grand River, Nebraska and farther north) and the Bitter 

 Creek series (including beds of Black Buttes, HallviUe, Medicine 

 Bow, Carbon, Point of Rocks, the Rock Spring series and Wash- 

 akie Station) are, although both afford Dinosaurian remains, 

 Lower Eocene. 



That the Lignitic beds east of the mountains in Colorado are 

 the equivalent of the Fort Union group of the Upper Missouri, 

 and are Eocene; " also that the lower part of the group, at least 

 at the locality 200 miles east of Greeley, is the equivalent of a part 

 of the Lignitic strata of Wyoming." The Lignitic beds near 

 Golden, Denver, Colorado Springs, Oanon City, Raton Hills, are 

 placed in a table with those of the Fort Union group ; but are 

 not afterwards remarked upon. 



13. Age of Angiospermous plants referred to the Cretaceous. — 

 In my notice of a paper by DeCandolle, on pp. 44^7-449 of this vol- 

 ume, I remark that the " Cretaceous plants of the United States 

 are the plants of beds which had previously been determined, 

 through the animal fossils, to be Cretaceous." This statement 

 needs, as I find, some modification. It is a fact that the plant- 

 bearing beds of the Lower Cretaceous of New Jersey and the 

 Rocky Mountain region have been referred to the Cretaceous for 

 stratigraphical reasons; and those of New Jersey on this ground, 

 long before the plants were found. But the chief evidence in favor 

 of this reference in the Rocky Mountain region was, as I learn 

 from Dr. F. V. Hayden, who has been prominent in collecting the 

 facts, the existence of Angiospermous leaves, the animal fossils 



