ART. XXXVI.-PALEONTOLOGICAL PAPERS NO. 8: REMARKS 

 UPON THE LARAMIE GROUP. 



By O. a. WniTE, M. D. 



In other writings* I have shown that all the principal brackish- water 

 deposits of the Western Territories are properly referable to oue great 

 group of strata which represents a period of time whose importance in 

 the geological history of the North American continent increases with 

 our knowledge concerning it. The members of the Laramie Group as 

 now understood are the Judith Eiver and Fort Union beds of the Upper 

 Missouri Eiver region ; the Lignitic Series east of theEocky Mountains 

 in Colorado ; the Bitter Creek Series of Southern Wyoming and adjacent 

 parts of Northwestern Colorado, and the " Bear Eiver Estuary Beds", 

 together with the Evanston Coal Seriest in Bear Eiver Valley and their 

 equivalents in adjacent parts of Wyoming and Utah. These, at least, 

 are the best-known members of the Laramie Grouj) ; but it has a much 

 wider geographical extent than even the widely separated localities just 

 referred to would indicate. Some of the known portions of this great 

 group doubtless represent different stages of the Laranjie period, but 

 the members just designated are, as a rule, understood to represent dif- 

 ferent geographical developments of its strata with modifications of its 

 fauna, rather than separate successive epochs of time in the geological 

 period which is represented by the whole great group. The proof of 

 the identity of these widely separated portions of the Laramie Group 

 consists in the recognition of various species of fossil mollusks in all of 

 them that are also found in some one or more of the others, tbus con- 

 necting the whole by faunal continuity. Similar proof has also been 

 obtained by Professor Cope in the discovery of certain species of verte- 

 brate fossils in more than one of these geographical members of the 

 Laramie Group. 



The entire geographical limits of the Laramie Group are not yet fully 

 known, but its present ascertained extent may be stated in general terms 

 as from Southern Colorado and Utah, northward into the British Pos- 

 sessions ; and from the meridian of the Wasatch Eange, eastward, far 

 out on to the great plains. Its extent north and south is thus known to 



*See Bull. U. S. Geol. and Geo^. Surv. Terr. Vol. IV, Art XXIX, and An. Eep. U. S. 

 Geol. and Geog. Sarv. Terr, for 1877. 



t Sometimes called the "Almy Mines'', from the name of the small mining hamlet 

 wheie the mines are located. 865 



