66 Kansas Academy of Science. 



though the upper strata contained forms very different from them 

 and closely similar to, though not identical with, well-known forms 

 from the true Dakota elsewhere.^ 



In 1895 Cragin showed that some of the invertebrates in the 

 Dakota beds at Mentor, southwest of Salina, Kan , were identical 

 with some in the Kiowa shales in the Comanche, in the southern 

 part of that state. These were partly the same as those which Meek 

 had described from that locality and referred to the Dakota in his 

 final report on the invertebrates of the Cretaceous. 



In 1896 T. W. Stanton stated that he had no doubt that the 

 Mentor beds are the equivalent of the Comanche, for not only in- 

 vertebrate fossils but plants harmonize with that view.^ 



Prosser expressed a similar conclusion, and claimed as additional 

 evidence that Cope had provisionally referred teeth found in the 

 Kansas Dakota to Lepidotid fishes, and stated that he had never 

 found Lepidotid fish remains in the Upper Cretaceous of North 

 America, while they were characteristically Lower Cretaceous and 

 Jurassic in Europe. He also stated that the Mentor invertebrates 

 are from either the same or higher beds as some which have fur- 

 nished plants characteristic of the Dakota.^ 



In 1901 Darton, in his report on the Black Hills, following the 

 decisions of Ward, proposed to separate the original Dakota of 

 Hayden into three formations — the Lakota, the Fuson and the 

 Dakota, the last being the upper third of the original. This he 

 placed in the Upper Cretaceous, while the others were considered 

 Lower Cretaceous. As he states it, "the sandstone formerly desig- 

 nated 'the Dakota sandstone,' or 'Cretaceous No. 1,' has in the last 

 few years been found to comprise not only a formation carrying an 

 Upper Cretaceous flora, but an extensive series of Lower Cretaceous 

 deposits as well. Accordingly, the term Dakota has been restricted 

 to the upper sandstone, containing the Upper Cretaceous flora, 

 while the much thicker, lower series has been separated as Lower 

 Cretaceous ; and as it consists of several stratigraphic units, these 

 will be differentiated here as separate formations."^ 



In 1905 Grabau brought ouj; the principle of overlap, transgres- 

 sive and regressive, and applied it to the Dakota formation, among 

 others. After a lengthy and lucid discussion, he sums up as fol- 

 lows : 



"The interpretation of these sections, in the light of the princi- 



2. Journal of Geolotry. vol. II. p. 263. 



3. Letter to Prosser quoted, K. U. Geol. Survey, vol. II. p. 190. 



4. Ibid, p. 192. 



5. U. S. G. S.. 21st Ann., part IV, p. 526. 



