274 GENERAL REMARKS. 



but species of the first seven named genera have been described in the 

 Flora of the old Tertiary. Even Liriodendron has many specific forms 

 already known in the Cretaceous Dakota Group. It is therefore rational 

 to admit that remains of these genera have not as yet been found in the 

 American Miocene, though they have been represented in that formation; 

 for they are in that of Europe. The same may be said of Azalea, two 

 species of which are described from the Oligocene of Florissant, and 

 perhaps also of JEsculus, though no remains of the last genus have been 

 remarked thus far in the geological floras of this continent. Cephalanthus, 

 Kahnia, and a number of others have not yet been found fossil anywhere: 

 they may be of more recent origin or of later introduction; or, owing to 

 peculiar circumstances of habitat, their remains may not have been pre- 

 served. And also it must not be forgotten that the relationship between 

 the floras of two geological epochs cannot be so intimate that the links 

 between the vegetable group can always be clearly followed. 



The difference between the vegetation of the present epoch and that 

 of the Miocene time is far greater in Europe than it is in America, though 

 in Europe the Miocene Flora is now much better known than it is on this 

 continent, where vegetable paleontology is still in its infancy. Some years 

 ago, when the fossil Flora of America was as yet unknown, it was contended 

 that the European Miocene Flora having its principal traits of analogy in 

 the living Flora of the North American continent, where most of its types 

 are reproduced, these had been derived, at the end of the Miocene period, 

 by migration through the fabulous Atlantis. The typical analogy is now 

 clearly explained by the affinity of the character of the Miocene Flora of 

 both continents; for, as seen from the table, the distribution of the more 

 important of its vegetable types is equally marked on both sides of the 

 Atlantic. As species in common, there are in the Ferns, Lastrea Fisclteri; 

 in the Conifers, Taxodium distichum, ijli/ptostrohus Europceus, Sequoia Langs- 

 dor fii ; in the Monocotyledons, Smilax grandifolia; in the Dicotyledons, 

 two species of Myrica, two of Bet/da, one each of Alnus, Carpinus, Corylus, 

 three of Fagus, one of Castanea, four of Qiiercvs, ten of Salix and Populus, 

 and so on: so that, of the 240 species of the American Miocene, more than 

 50 are identified in that of Europe; and besides, a large number of others 

 are so closely related that the specific differences are scarcely noticeable; 



