wAKi..] DISCUSSION OF THE TABLE. 527 



tbe Eoceue ; but such evidence is Tery feeble. Vitis is a strong Laramie 

 geuus, but it occurs sparingly in tlie Eocene. It therefore scarcely 

 belonj^s in this list. Zizyphus (litters from the other two prominent 

 rhamnaceous genera, Ehamnus and Paliurus, in extending into the Eo- 

 cene. It is a fair representative of the class we are now considering 

 that indicate a resemblance between tlie Laramie and the Eocene floras. 



The Celastracese are highly characteristic of the Eocene, and one 

 form which has been distinguished as Celastrinites is found in the 

 Laiamie. The Eocene species of this genus are all from Sezanne, and 

 furnish another evidence of the truth of Mr. Lesquereux's statement in 

 his " Cretaceous and Tertiary Flora" that the flora of the Laramie re- 

 sembles that of Sezanne more closely than it does that of the Eocene 

 proper. A still more striking illustration of the same fact is found in 

 Grewiopsis, which is the Paleocene form of the Miocene genus Grewia^ 

 also occurring in the Laramie. 



Dombeyojisis is one of the best marked Eocene genera, but it is al- 

 most exclusively confined to Monte Bolca. Its occurrence in the Lara- 

 mie group is a singular fact and one that has often been brought for- 

 ward in support of the Eoceue age of that group. 



The Magnoliacete are a very ancient type of plants, species of Lirio- 

 dendron being abundant in the Cenomanian. The genus Magnolia, 

 which occurs in the upper Cretaceous beds of the Peace and Pine 

 Rivers in British America, is abundant in both the Laramie and the 

 Eocene. It is simply a persistent type. 



We have thus rapidly run over the evidence furnished by these two 

 classes of genera for and against the view that the Larauiie flora bears 

 such a resemblance to the Eocene flora as to suggest the substantial 

 synchronism of the two series of deposits. It is perhaps best to leave 

 the reader to form his own judgment as to the result, but in the light of 

 former discussion of this question the caution against mistaking hori- 

 zontal for vertical distribution, may not be out of place. In the great 

 majority of cases, as has been pointed out under each genus, the types 

 persist through difterent ages in the same or adjacent parts of the 

 the world, and the absence of Laramie types in the Eoceue, and vice 

 versa, is due to the wide geographical separation of the beds of the 

 two formations. Closer study of the table will show that most of 

 the European genera can be traced from the Cenomanian up to the 

 Miocene of that continent, while most of the American genera can be 

 traced from the Dakota group up to the Miocene of Alaska and Green- 

 land. That some genera should be common to both hemispheres was 

 to be expected, but that these distinctly argue either the Eocene or the 

 Cretaceous age of the Laramie beds cannot be reasonably maintained. 



This is the proper place, before descending to specific details, to con- 

 sider this interesting subject of geographical distribution in its relation 

 to the present plant life of the globe. The present distribution of vege- 



