RELATION OF THE GRAVELS TO AFTONIAN INTERVALS 343 



by Shimek in the article cited, the beds contain the shells of river mol- 

 lusks belonging to species still living in Iowa ; all the evidence shows that 

 the climate was comparatively mild, and that the streams which carried 

 and distributed the fluvial deposits, the streams which transported the 

 mammalian remains and distributed the shells of the river mollusks, were 

 not a product of melting pre-Kansan glaciers. The mammals are repre- 

 sented by bones and teeth in such numbers, in such a state of preservation, 

 and are found at so many widely scattered exposures along different 

 stream valleys as to make it certain that they are not mere chance inclu- 

 sions washed out of preexisting drift or out of preglacial deposits. It is 

 worthy of note that the mammals consist of large herbivores. There are 

 horses of at least two different species, one species of camel, the great 

 stag, Cervalces, two elephants, the common Pleistocene mastodon, and at 

 least one large Edentate, Mylodon. There are bones and fragments of 

 bones that have not been identified. The great quantity of well preserved 

 material would imply that the uplands between the stream valleys were 

 densely populated, for only a small proportion of the animals that lived 

 and died in the region would be represented by skeletons coming within 

 the reach of floods. To supply these great herbivores with food required 

 an abundance of vegetation such as could not be developed until some 

 time after the pre-Kansan ice and all its climatic effects had disappeared 

 from southwestern Iowa. 



Localities 



The fossil remains under consideration have come, almost exclusively 

 from the western slope of Iowa, the Aftonian beds having been exposed 

 in the process of valley-making by the streams draining into the Missouri 

 river. It is now known that Aftonian deposits occur at intervals all the 

 way from Sioux City to Hamburg, but the valleys which have thus far 

 received the greatest attention are those of Maple, Little Sioux, Soldier, 

 and Boyer rivers. Gravels have been worked on a commercial scale along 

 the Boyer, and mammalian remains have been uncovered at Denison, 

 Logan, and Missouri Valley. At the point last named the most impor- 

 tant is the Cox pit, which, by reason of the greater amount of work done 

 in it, has furnished the larger number of the specimens referred to in this 

 paper (plate 16, figure 1). 



The Peyton gravel pit, located about a mile southwest of Pisgah, has 

 been the most productive of the Aftonian exposures in the valley of the 

 Soldier river (plate 16, figure 2). In the bluff on the east side of the 

 Little Sioux river, a few rods south of the Monona-Harrison county line, 

 there is a fine exposure of Aftonian gravels which has been worked inter- 

 mittently and chiefly for road materials. Nothing is known of the find- 



