420 



SCIENCE. 



[N. S. Vol. V. No. 115, 



his list a great many doubtful fragments ; 

 but when the floras of the Aachen beds and 

 those of the claj's of New Jersey shall be 

 fully studied and illustrated it will undoubt- 

 edly be found that the botanical aspects are 

 the same, and that there are perhaps as 

 many species identical in the two forma- 

 tions as in those of Greenland and New 

 Jersey. Hence, 'iue may fairly infer that the 

 collections of plants from the New Jersey clays, 

 the Dakota group, the Patoot and Atane beds of 

 Oreenland, the Aachen series of Germany, and 

 the plant-hearing Cretaceous rocks of Bohemia 

 fairly represent the vegetation of the loorld dur- 

 ing the middle and latter portions of the Creta- 

 ceous age." 



I do not wish to conceal the fact that Dr. 

 Newberry's views are somewhat extreme 

 in the direction of raising the Amboy Clays 

 up to a level with the Dakota group of the 

 West and the Aachen and Atane beds. My 

 own explanation has always been that the 

 Greenland beds are simply the northeastern 

 extension of the Amboy Clays and Island 

 Series, but that they may nevertheless rep- 

 resent a somewhat higher horizon in the 

 same way that the Amboy Clays are higher 

 than the Older Potomac of Maryland and 

 Virginia, although belonging to the same 

 general belt, either through the destruction 

 of the lower members of the formation or 

 because the continent at those points was 

 out of water while the Virginia beds were 

 in process of deposition. On this theory it 

 would be perfectly natural that a large 

 number of Amboy Clay species should 

 have survived with little change into the 

 slightly more modern period at which the 

 Atane beds were deposited. In confirma- 

 tion of this, and against the view of the 

 great similarity between the Amboy Clay 

 flora and that of the Dakota group, I have 

 shown that most of the species common to 

 the two are such as Professor Lesquereux, 

 in studying the Dakota group, identified 

 with Greenland forms, and I have also 



shown that, in a few cases at least, such 

 identifications were not justified.* I there- 

 fore still think that the Amboy Clays, in- 

 cluding the Island Series, are lower than 

 Cenomanian, but any attempt to place them 

 below the extreme summit of the Lower 

 Cretaceous would, in the light of these 

 facts, involve assumptions too violent to be 

 entertained. 



It certainly cannot be justly said that all 

 this evidence, because derived from fossil 

 plants, is without value. The floras, both 

 of the Older and Newer Potomac, are alto- 

 gether too rich and too definite to be disre- 

 garded. Taken as a whole they show as 

 well marked diSerences in the character of 

 the vegetation as could be desired. It is 

 true that geologists and paleozoologists are 

 generallj' unprepared to weigh the evidence 

 from fossil plants, but in this case they need 

 not know the specific nature of the plants. 

 It is sufficient to compare the illustrations, 

 say, of The Flora of the Amboy Clays, with 

 those of The Potomac or Younger Mesozoic 

 Flora. t They may be regarded simply as 

 pictures, and it requires no practiced eye to 

 discover that they are utterly unlike. A 

 child would readily perceive the diflerence 

 between a plate illustrating the ferns, cy- 

 cads, and conifers of the Older Potomac 

 and one illustrating the broad dicotyle- 

 donous leaves of the Amboy Clays. The 

 contrast would be still greater if made with 

 any of the true Jurassic floras of the world, 

 as, for example, that of France, so profusely 

 illustrated by the late Marquis Saporta in 

 eight volumes containing 300 plates. J It 

 therefore seems to me that the two works 

 now before us, together with the eai-ly illus- 

 trated one of Professor Fontaine, furnish 



* The Potomac Formation. 15th Ann. Kept. U. 

 S. Geological Survey, pp. 373-374. 



t Monographs of the XJ. S. Geological Survey, 

 Vol. XV., plates. 



% Paleontologie fran^'alse. V(^'getaux. Terrain Ju- 

 rassique, par le Marquis de Saporta, 4 vols, each of 

 text and atlas, Paris, 1873-1891. 



