Marsh Collection, Peabody Museum. 427 



the two continents are very similar. He says,* " We should 

 not, of course, expect the species to be common to any great 

 extent, and the comparison is practically limited to the genera. 

 Looked at from this point of view, we see that the resemblance 

 is indeed close, a great number of the important genera occur- 

 ring in both floras. There are no less than 46 of these common 

 to the two, though in some cases the author's individuality is 

 probably alone responsible for slight differences in the ter- 

 minations in the names." What is here said of the plant 

 remains from the lower beds is also true of those from the 

 Cenomanian, and in fact the entire Cretaceous flora of the two 

 Hemispheres is strikingly similar. 



The second fact of unusual importance is the sudden intro- 

 duction of the higher Angiosperms in the several strata in 

 which they occur. They first make their appearance in beds 

 below the Cenomanian, but with very few exceptions these 

 species are all strictly representatives of, and belong to, the 

 higher forms. They exhibit few traces of a lower organiza- 

 tion, and certainly fall far short of the connecting forms we 

 should expect to find bridging the gap between the Dicotyle- 

 dons and lower types, if their evolution had taken place in the 

 regions where their remains are now found. It is possible to 

 explain the sudden influx of so extensive, varied, and highly 

 organized a flora as that of the Cenomanian only on the hypoth- 

 esis of migration, and this migration was, moreover, in all 

 probability due to a climatic change which permitted the 

 species to spread into new localities formerly unfitted for their 

 maintenance. There is no other way in which to account for 

 the remarkable similarity between the florae of the two Hemi- 

 spheres, it seems to me, than to assume the existence of a 

 common center of dispersion. All the facts in connection with 

 the distribution of these higher plants offer such a striking 

 analogy to a similar class of facts concerning the higher Mam- 

 malia, that I shall have occasion to recur to this subject again. 



In the Upper Cretaceous beds of both Europe and America, 

 the remains of a rich flora have been found. I can not better 

 illustrate the character of this flora in America than to quote 

 a few extracts from the work of Professor L. F. Ward, one of 

 the most eminent authorities on paleobotany in America. In 

 describing the types of the Laramie flora, he says,f in speaking 

 of the genus Ficus : " Among my Fort Union specimens I 

 have thus far found three species referable to that genus which, 

 if this reference is sustained, and if no others be detected, will 

 show that a climate existed in the Fort Union epoch and at 



* Some Analogies in the Lower Cretaceous of Europe and America. Six- 

 teenth Ann. Kept. U. S. Geol. Surv., p. 534, 1895. 

 fBuli. U. S. Geol. Surv., No. 37, 1887. 



