44: THE LEWIS BROOKS MUSEUM. 



tion of them to particular parts of the earth. We have in 

 Virginia two series of beds which contain vegetation of the 

 Mesozoic type. The older of these floras is contained in the 

 Richmond coal field. The plants are quite numerous and 

 plainly indicate that the age of the beds is Rhaetic or lower 

 Lias, the period succeeding the Trias, the oldest of the Me- 

 sozoic eras. The younger flora is found in the beds at 

 Fredericksburg, and appears to be a little older than that 

 of the lower Cretaceous. Many most interesting plants 

 occur here, and promise to throw much light upon the veg- 

 etation of that ancient period. It is mainly tropical in 

 type, and seems to contain several well marked angiosper- 

 mous plants. If this proves to be the case our Fredericks- 

 burg beds will contain the oldest known plants of this most 

 important modern type. Most Geologists regard all these 

 Mesozoic beds in Virginia as Triassic, but do so erroneously, 

 and notwithstanding the correct interpretation of them 

 made long ago by Professor Rogers. The appearance of 

 angiosperms in America sooner than in Europe is in accord- 

 ance with the general law that has been established, which 

 is, that the vegetation of the American formations is older 

 than that of the European. In the Dakota beds of the 

 western part of the United States, which correspond with 

 the middle Cretaceous of Europe, many of the most inte- 

 resting genera of trees and shrubs, which now abound in 

 our forests, made their first appearance. Since this ancient 

 period, strange to say, these plants have undergone but lit- 

 tle modification in type, though many of them are greatly 

 reduced in the number of their species. Many of them also 

 show evident indications that they are about to pass awa} 7 . 

 It is a singular fact that, although in other parts of the 

 world the plant life has changed many times since this 

 Cretaceous period, we still find in eastern North America, 

 and in eastern Asia, forms which are contained nowhere 

 else, and which are but little changed from their Cretaceous 

 prototypes. Owing to the survival of a remnant of this 



