52ti FLORA OF THK LAKAMIK GROFP. 



we are considering, while Viburnum is, next to Populus and Platanus, 

 the largest and most characteristic of that class. With fifteen species 

 in the Laramie, four in the Senonian, and the two Eocene species from 

 the lowest beds of that age, it seems to be a very ancient type, and one 

 which goes far to separate the Laramie flora from that of the Eocene. 



If there were no cases which could be cited to offset this array of evi- 

 dence, it might seem that no two floras could be more distinct than those 

 of the Eocene and the Laramie, but as we pass rapidly down the op- 

 posite column we shall see that there certainly are some bonds of union. 



It was long maintained that the peculiar fucoids called Halymenites 

 were; characteristic of the Eocene, being so abundant in the Flysch of 

 Switzerhmd, and their presence in the Laramie strata was put forward 

 as a proof of the Eocene age of that group, but they are now known to 

 occur in the Cretaceous, though absent from the Senonian beds, and as 

 low as the Jurassic. They also extend upward to the Miocene. 



The two species of Caulinites from the Laramie difler widely from 

 those of the Paris Basin, but probably belong to that type of plant and 

 in so far assimilate the Laramie to the Eocene flora. It is, however, 

 the palms that have been chiefly relied upon to establish the Eocene 

 character of the Laramie. The evidence here must be admitted to be 

 strong, and their absence from the Senonian beds serves to add to its 

 force. The Eocene was the age of palms. The numerous fruits refer- 

 able to that family found in the London clay and also at Monte Bolca, 

 constitute one of the leading features of the flora of that epoch, and 

 these are in a manner paralleled in some parts of the Laramie, notably 

 in the tufa beds at Golden, by the many nut-like bodies which Mr. 

 Lesquereux has designated by the term Palmocarpon. But aside from 

 these, and probably from the same trees that bore them, we have four 

 species of Sabal and two of Flabellaria represented by leaves in the Lar- 

 amie flora, though nearly all these palms are found in the lower districts. 

 It is only this lower Laramie that has been claimed as Eocene, and if 

 we restrict the term to this flora its afduity to that of the European 

 Eocene is greatly strengthened. 



The genus Alnus is well represented in the Eocene, especially in the 

 Paleocene, and one abundant species is found in the Laramie group. 

 The Senonian species is from Greenland and may have been the ])rogen- 

 Itor of the wide spread arctic form A. Kifer.steinii, Gopp., so celebrated 

 in the Miocene beds of the North. 



The Marquis Saporta flnds eight species of Ehus in the gypsum beds 

 of Aix in Provence, and the geuus also occurs in all the Laramie hori- 

 zons. The type therefore is common to the two formations and serves 

 to assimilate the two floras. The one Senonian species is from the 

 Quedlinburg beds. 



Sapiudus predominates in the Fort Union group and in various 

 Eocene localities, and in so fiir tends to identify the upper Laramie with 



