Kansas; marking exactly the limits and the characters of this group, now 

 generally admitted as the lower member of the American Cretaceous forma- 

 tion. 



Vegetable paleontology has been too often considered as of little import- 

 ance in regard to the determination of the age of geological divisions. In 

 this case at least we have an evident proof of its value as a guide ; for, indeed, 

 without the fossil leaves of Nebraska, the. relation of the Dakota group either 

 to the Trias, the Jurassic, or the Cretaceous, would be still uncertain and 

 subject to dispute ; especially for the reason that the few animal remains rec- 

 ognized in the red sandstones of this group have been, as yet, too scant and of 

 too little distinct characters to afford sufficient evidence on this point. This 

 proves the importance of the first collection of fossil plants of Prof. Hayden. 

 For now, as a result of his care in collecting them; in publishing geological facts 

 marking the exact relative position of the Dakota group to the Permian rocks 

 which underly it, and to the Cretaceous strata above it, and at the same time 

 forcing the examination and comparative study of these fossil plants, which 

 most of the geologists of the time would have passed as unworthy of regard ; 

 new researches have been induced; specimens have been obtained, more nu- 

 merous, more perfect; and we have not only full geological evidence in regard 

 to the lithology and geological distribution of the strata, but the first pages of 

 what may be called a new chapter of our geological history. To it have been 

 added the records furnished by the materials afterward brought up in abund- 

 ance from various points. 



The first contribution to these materials appears to have been furnished 

 by Doctor Newberry. In reporting his opinion on the general character of 

 the leaves submitted to his examination by Messrs. Meek and Hayden, he 

 adds this paragraph i 1 " I may say in confirmation of the assertion that your 

 fossil plants are Cretaceous, that I found near the base of the yellow sand- 

 stone series in New Mexico, a very similar flora to that represented by your 

 specimens, one species at least being identical with yours, associated with 

 Gryjrficea, Inoceramus, and Ammonites of Lower Cretaceous species." And 

 in his report on Doctor Hayden's fossil plants, he also remarks: 2 "That he 

 subsequently went himself to the region where the vegetable remains had 

 been obtained, and that he spent some years in the study of the geology of 

 the interior of the Continent, exploring a large area occupied by Cretaceous 



1 American Journal of Science anil Arts, vol. xxvii, No. 71), p. 33. 

 -Notes on the later extinct floras of North America, p. A. 



