22 THE FLORA OF THE DAKOTA GROUP. 



for by a diflFerence in the horizon of the strata where they have been found 

 and therefore by a diiference of age. Are there pecuHar zones in the forma- 

 tion which miglit be indicated by marked characters in the vegetation I 

 No answer can as yet be given to the question. The concretionary speci- 

 mens mentioned above have been found on the so-called highlands of Ells- 

 worth County. But what are those highlands as compared in altitude to 

 the lowlands f Prof Mudge, who has closely searched for the distribution 

 of the remains of plants in Kansas, did not find any differences in the char- 

 acter of the plants that seemed to depend on the altitude of the hills. He 

 recognized leaves of the same species from the top to the bottom of wells 

 40 feet deep. Near Salina, at a locality mentioned in Cret. Fl., p. 30, I have 

 found the same species of vegetable remains distributed from the base to the 

 top of the hills, the altitude being about 75 feet above high-water mark of 

 the river. Hence, it is not possible, as yet, to consider a difference in the 

 vegetation by peculiar zones like those in the Quadersandstein or Middle 

 Cretaceous of Europe, where the zones of the Liriodendron or those of the 

 Credneria are mentioned as marking the relative horizons of the strata. 



The specimens of leaves or fragments of vegetation described below 

 have been collected by Mr. Charles H. Sternberg for the Museum of Com- 

 parative Zoology of Cambridge, Massachusetts, by Mr. J. C. Mason for the 

 cabinet of Mr. R. D. Laooe, of Pittston, Pennsylvania, and later by Mr. 

 Ambrose Wellington and Judge E. P. West for the museum of the Univer- 

 sity of Kansas. Prof F. H. Snow, of the University of Kansas, has also 

 furnished important assistance by the conununication of a number of speci- 

 mens from his cabinet of all found in Kansas, and Prof N. H. Winchell, 

 State geologist of Minnesota, has authorized the description of a few spe- 

 cies represented by specimens obtained by the survey of that State in 

 the same formation. Quite recently a large collection of fossil plants of 

 the Dakota Group, made in Kansas by Mr. Sternberg, has been added to 

 the above. 



