436 IM-ORA OF THE LARAMIE GROUP. 



It is therefore truly surprising to learn that " several of the species 

 found in the brackish-water layers at the base of the Bitter Creek 

 group are closely related to species found in similar deposits in Slavonia 

 and referred to the Eocene Tertiary by Brusina.'" 



With regard to vertebrate remains, this objection does not apply, and 

 could they be made to harmonize with themselves they might, perlia])s, 

 be trusted to some extent as indices of synchronism in widely separated 

 localities. But, as shown by Cope, they do not thus agree, for the Lara- 

 mie forms include genera that are regarded as characteristic of Creta- 

 ceous and others that are regarded as characteristic of Tertiary strata. 

 This should surjirise no one. The law that has been laid down by 

 paleontologists, that the same epochs in geologic time produced the 

 same living forms — which is the converse of the assumption commonly 

 acted upon, that tlie occurrence of the same forms proves the beds 

 containing them to be of the same age — is contrary to the now well 

 established priiuiiples of geographical distribution, according to which 

 the earth is subdivided into a large number of faunal areas more or less 

 clearly marked off one from another. The peculiarity of this principle 

 whi(di is of most importance to paleontology is that these territorial 

 subdivisions re])resent faunas not merely different from one another, 

 but showing different degrees of biologic development as development 

 is su])posed to have gone on in the animal kingdom. Every one knows 

 that the fauna of Australia belongs to an undeveloped type, being 

 marsupial in aspect so far as its mammals are concerned. The types 

 of South America are lower than those of North America, and the lat- 

 ter lower than those of Asia and Europe. If all the present faunas of 

 the globe were buried under its soil it is clear that it would not only 

 be impossible to harmonize the deposits of different continents, but 

 that the inference now freely drawn by paleontologists that the less 

 developed forms demonstrate their existence at earlier epochs would 

 lead to grave mistakes and be generally false. New Zealand is now in 

 its age of birds, while the Galapagos Islands are still in that of reptiles, 

 or the Mesozoic age. 



VEGETATION OF THE LARAMIE AGE. 



Confining ourselves, then, for the future to the other kind of land 

 life and the only remaining form of life, that of plants, we may look at 

 the (piestion of synchronism by the light of this class of data from the 

 same general point of view as we have done by the light of the two 

 kinds of animal life which we have Just considered. And, tiist, what 

 ouglit we to expect the flora of the Laramie group to teach respecting 

 the synchronism of its dei)osits with those of other parts of the world? 

 Clearly, as in the land vertebrate life, there is no si)ecial obstacle to this 

 form of inquiry, such as the invertebrate aquatic life presents, arising 



' Dr. White, in " Geology of the Uinta Mountains," p. 86. 



