Mesozoic and Ccmnozoic Geology and Palceontology. 201 



the separation has not been maintained, and the authors, instead of 

 extending the Fort Union Group to include these rocks, have called 

 both the Fort Union and Bear River Groups the Laramie Group. 

 Prof. White, and some other authors,, call the rocks Post-Cretaceous. 

 This is not objectionable, because it is treating them with reference to 

 their geological position, and not proposing a new name for a group of 

 rocks. If it is desirable to retain the name Bear River Group, it should 

 be applied to the rocks below the Fort Union Group, and in no event 

 can the Fort Union Group be swallowed up by another name for the 

 same group of rocks. A great many s3^nou3'ms have been proposed for this 

 Group, some of which it is difficult to wipe out, and others will burthen 

 the science for a longer or shorter period, but, finall}^ we may hope for 

 their burial in oblivion. Any one can propose to call an exposure of 

 rocks, at any place, by a new name, but it requires a palaeontologist to 

 determine the age of the rocks and to refer them to their proper posi- 

 tion in the geological column. A little reflection, therefore, will satisfy 

 the reader, that proposing a new name for a group of rocks, wherever 

 exposed, without giving the palseontoiogical reasons for so doing, i« an 

 evidence of ignorance, and most frequenth' w^e find those who do it are 

 suffering from downright stupidity. 



The plants which have been described,! from the Cretaceous rocks in 

 question, have been referred to about 150 genera, and number about 500 

 species. About 50 of these genera are now extinct, and about 100 are 

 living. The larger part are from the Fort Union Group of the West, and 

 from their intimate relation with living forms, the great palseo-botanist. 

 Prof. Lesquereux, referred the rocks to Eocene age. The testimony, 

 howcA^er, of the animal remains, which Prof. Cope was the first to dis- 

 cover, has proven that they must be referred to the upper or later 

 Cretaceous. This determination has, if we may trust investigations 

 of our fossil botanists, specifically united the Cretaceous era with the 

 present time. For the living plants. Coryhts americana, C. y^ostrata^ 

 DavalUa tenulfoUa, and Onoclea sen.^ihilis have been identified among 

 the fossils from the Fort^ Union Group. It is likely that too much 

 confidence in this identification ma}^ lead to error, for as yet we may 

 fairl}' suppose that we know but little of the vegetable life of this vast 

 period of time in comparison with what will be known in a few de- 

 cades. And better specimens than those upon which the identifica- 

 tions have been made may show specific distinctions. It is sufficient 

 that the forms so much resemble the living as to be mistaken for 

 them, tc show how closely the living forms are connected with the 

 ancient dead. 



