BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



VOL. 20, PP. 341-356, PLS. 16-27 OCTOBER 11, 1909 



AFTONIAN MAMMALIAN FAUNA 1 



BY SAMUEL CALVIN 



(Presented by title before the Society December 31, 1908) 



CONTENTS 



Page 



Strati graphic position of the Aftonian deposits 341 



Relation of the gravels, in time, to the Aftonian interval 342 



Localities 343 



The Aftonian horses 344 



Other Ungulates 350 



Proboscideans 351 



Elephants 351 



Elephas imperator Leidy 351 



Elephas primigenius and E. columbi 351 



Mastodon : Mammiit americanum 352 



Other Proboscidean remains 352 



Edentata 353 



Megalonyx 353 



Mylodon 353 



Correlation 353 



Postscript 354 



Stratigraphic Position of the Aftonian Deposits 



Between the two older drift sheets of Iowa, known respectively as the 

 pre-Ivansan and the Kansan, there are many evidences of a long interval 

 of mild climate. Such an interval is indicated by intercalated weathered 

 zones, soil bands, peat beds, buried forests, and aqueous deposits of sand 

 and gravel. Chamberlin pointed out the interglacial position of the ex- 

 tensive gravel beds at Afton Junction and Thayer and gave the name 

 Aftonian 2 to the interval which they in part represent. The writer, dis- 

 cussing the age of these gravels in the Proceedings of the Davenport 

 Academy of Sciences, was led to conclude that they are the work of 



1 Manuscript received by the Secretary of the Society December 31, 1908. 



2 See Journal of Geology, vol. iii, 1895, p. 272. When this editorial was written 

 it was believed that the till beneath the gravels was the Kansan and that above them 

 the Iowan. For later discussion and reference of the gravels to their true position be- 

 neath the Kansan, see the same journal, vol. iv, p. 872. 



XXX — Bull. Geol. Soc. Am., Vol. 20, 1908 (341) 



