WARI..1 DISCUSSION OF THE TABLE. 525 



No coniferous form is more abundant in the Laramie than Sequoia, 

 six species of which are distinguished. Of the nine si)ecies from upper 

 Cretaceous strata all but one are found in the western hemisphere. This 

 furnishes an excellent illustration of the extent to which certain types 

 persist with modification in the same or adjacent territorial areas. There 

 is no doubt that should ui)per Cretaceous beds be found within the 

 United States these forms will occur as the direct ancestors of the Lara- 

 mie species. Their rarity in the Old World is seen also to be a fact of 

 geographical and not of geological significance, for it is true of both the 

 Cretaceous and the Eocene. 



The genus Taxodium, two of the species of which are so abundant in 

 the Laramie, Senonian, and Miocene, is curiously scarce in the Eocene, 

 and therefore claims a place in our first column. 



It is in the Gymuosperms, therefore, that those characters appear 

 which give to the Laramie flora such a strong Cretaceous facies. We 

 find this quite otherwise in the next group, the Monocotyledons. Only 

 in one genus (Phragmites) of this subclass do we find the Eocene want- 

 ing. This genus occurs abundantly in the Laramie, and the only Seno- 

 nian species reported is from the Pacific coast of America, so that it 

 seems that in pre-Miocene time the type was confined to the western 

 hemisphere. 



It is, however, among the Dicotyledons, and chief!}' in the Amentaceae, 

 that the most notable examples occur to show the similarity of the Lar- 

 amie to the Senonian flora, and also its unique character as compared 

 with any other formation. Its 23 species of Pojiulus form one of the 

 greatest of its anomalies, and stamp it with a sjiecial character. The 

 nine species of the Senonian cause that formation to partake somewhat 

 of this character, but when we see that all but two of these come from 

 the Vancouver beds or from Greenland we see that this is a distinctly 

 American type. 



The genus Juglans, with its eight Laramie, one Vancouver, and one 

 Patoot species, is of special interest in the light of the numerous forms 

 of Carya and Juglans which persist in the American flora. The fossil 

 forms of Juglans may well have been the ancestors of our hickories as 

 well as of our walnuts. 



Neither of the two last-named genera, however, can claim as great a 

 share of our interest as does the genus Platauus. With its eight Lara 

 uiie and two Greenland species, and its entire absence from the Eocene, 

 it seemed to constitute in pre-Miocene time one of the characteristic 

 vegetable types of America. 



Passing over the two polypetalous genera, Cornus and Acer, which in 

 like manner belonged during this epoch almost entirely to the west, we 

 come to Ehamnus, with twelve Laramie species ; one of the Senonian 

 species is also western (Patoot). Paliurus is an allied genus and is 

 similar in its range to Rhamnus. 



Of gamopetalous genera, Fraxinus, though small, belongs to the class 



