120 B. SHIMEK AFTONIAN FOSSILIFEROUS GRAVEL AND SAND BEDS 



Page 



17. Cox pit 135 



18. Peckenpaugh sections 136 



19. Denison pit 137 



20. Offerman pit 138 



21. Gladwin section 138 



22. Mad Creek section 139 



Are the fossils Aftonian? 139 



Conclusions 140 



Previous Discussions 



About a year ago the writer announced^ the discovery in western Iowa 

 of Aftonian sands and gravels containing mammalian and mollnscan 

 remains. 



Subsequently Calvin included a brief discussion of the same deposits in 

 his presidential address/ and in the same volume* described the mam- 

 malian fossils in detail. 



In none of these papers was an effort made to present the full evidence 

 on the basis of which the reference to the Aftonian was made, and the 

 correctness of this reference has been questioned recently in private cor- 

 respondence. 



At the December, 1908, meeting of the Geological Society of America 

 the writer presented a paper, ^ the publication of which was somewhat 

 delayed,® in which this question was discussed to some extent, but no 

 special emphasis was placed upon the fossiliferous portions of the forma- 

 tion. 



Importance oe the Aftoxian mammalian Fauna 



correlation with other deposits 



The discovery of a distinct Aftonian fauna is not only of interest and 

 value in itself, but it has an important bearing on a number of interesting 

 questions. 



Thus it may 'make possible the closer correlation of formations like the 

 Equus beds, Sheridan beds, etcetera, which contain practically the same 

 mammalian fauna. 



EVIDENCE OF CLIMATIC CONDITIONS 



"Moreover, the presence of this fauna makes possible for the first time 



a Science, vol. xxviil, 1908, p. 923. 



•BuU. Geological Society of America, vol. 20. 1900. pp. 137-130. 



*Ibid., pp. 341-3.50. 



"5 Read by title. 



« Bull. _ Geological Society of America, vol. 20, 1909. 



