LOCATION, CHARACTER, AND FAUNA OF THE SECTIONS 259 



brates consisting largely of Comanche species, with, a few from the typical 

 Dakota fauna. Logan's stratigraphy and paleontology of the upper part 

 of the Dakota was adopted by Twenhofel 7 and apparently forms the chief 

 basis for his conclusion that the Dakota is Comanchean. Logan's failure 

 to mention any localities at which his fossils were collected made it im- 

 possible to check his results in the field, and I therefore wrote him under 

 date of October 11, 1905, inquiring about the localities from which he 

 obtained the "upper Dakota" fossils listed in his report, saying that "the 

 matter is of immediate interest to me now, in connection with recent field- 

 work, and I write to ask whether, after so many years, you can give me 

 exact localities and horizons for the Dakota invertebrates you have listed ; 

 also, whether the collections are still at Lawrence, assembled by horizons 

 and localities, and to whom I should apply to borrow them for brief ex- 

 amination." 



Professor Logan's reply of October 18, 1905, is in part as follows: 



"You will doubtless recognize the strong 'Mentor' phase of that list of fossils. 

 At that time I included the Mentor beds in the Dakota. Had I seen Professor 

 Prosser's paper 8 that list would not have been given as belonging to the Da- 

 kota. That I thought this horizon identical with the upper Dakota will be 

 seen from a statement to Prosser on page 189 of the same report. However, 

 those fossils spoken of as being similar to the Mentor fossils have never been 

 determined, to my knowledge. I think I sent them all to Prosser. . . . The 

 localities are : at Beloit, Mitchell County, just below the mill on Solomon River, 

 and at Denmark, Lincoln County, from rock taken from the lignite mines at 

 that place. The shells are abundant at this place. At Beloit they occur in 

 sandstone and are not abundant. 



"I have no doubt that some of my determinations of the Mentor fossils were 

 incorrect, but you will see by comparing with your own list on page 185 that 

 some are right." 



It is evident from this statement that the larger part, if not all, of the 

 fossil mollusks listed by Professor Logan as from the upper beds of the 

 Dakota really came from the Mentor horizon, probably in the area around 

 Marquette, where at that time he had erroneously assigned some of the 



7 W. H. Twenhofel : The Comanchean and Dakota strata of Kansas. Am. Jour. Sci., 

 4th ser., vol. 49, 1920, pp. 281-297. See especially pages 286, 287. 



s Charles S. Prosser : The Upper Permian and the Lower Cretaceous. University Geo- 

 logical Survey of Kansas, vol. 2, pp. 51-194. The statement on page 189 referred to in 

 Professor Logan's letter is included in the following quotation : "Mr. W. N. Logan has 

 also sent me Mentor fossils from the 'Natural corral' in McPherson County supposed to 

 be the same locality studied by Mr. Beede, among which are specimens of Trigonia 

 emoryi Con. Mr. Logan wrote me that he "had found fossils in the upper and middle 

 horizons of the Dakota which seem to be identical with the Mentor fossils.' From a 

 sandstone at the extreme upper limit of the Dakota near Beloit Mr. Logan has also col- 

 lected lamellibranch shells that have not been identified specifically and may possibly 

 belong in a different fauna from that of the Mentor." 



