RELATION OF rROBOSCIDEAN REMAINS TO NEBRASKAN GUMBOTIL 81 



Inteoduction 



Two tusks and some limb bones of a mammoth or mastodon were found re- 

 cently in the base of Kansan till which overlies Nebraskan gumbotil, about 

 four miles southeast of Osceola, Clarke County, Iowa. It is the purpose of 

 this paper to describe briefly the chief features of these remains and to indi- 

 cate the probable significance of their relationships. 



History of the Discovery 



In August, 1920, Messrs. Earl Cox and Sharon Warrick uncovered a tusk 

 when they were grading a north-south wagon road in the southern part of 

 the northwest quarter of section 3, Greenbay township. Later, at the same 

 place, Mr. Cox and Mr. Fred Stubbs began to excavate with the hope of find- 

 ing the other parts of the animal from which the tusk had come. They soon 

 dug up a second tusk and some limb bones. Unfortunately, on exposure, the 

 tusks and bones quickly disintegrated, so that when the place of discovery 

 was visited, in the month of October, it was possible to see only the fragments 

 of the remains and some of the molds of the bones in the clay from which the 

 fossils had been taken. Thanks are due Mr. Fred Stubbs for furnishing infor- 

 mation about the bones and for pointing out the positions which they had be- 

 fore they were removed. Professors A. C. Trowbridge, A. O. Thomas,, and 

 R. W. Chaney, of the Department of Geology of the State University of Iowa, 

 also visited the place of discovery. Each of these persons has ofi'ered helpful 

 suggestions in the preparation of this paper. 



The FoSvSils and their Relationships 



In all, two tusks, a scapula, a limb bone which was probably a humerus, 

 fragments of ribs, and some unidentifiable small pieces of bone were found. 

 Absence of teeth precludes with any degree of certainty the generic determina- 

 tion of the proboscidean. 



The fossils were imbedded in glacial till on the south slope of a hill about 

 100 yards from its base. A section taken along the wagon road from the base 

 of the gently sloping hill to its summit shows the following kinds of glacial 

 deposits : 



Feet 

 4. Glacial till (Kansan), oxidized, unleached along slope, inclusions of Ne- 

 braskan gumbotil near base, about 60 



3. Gumbotil (Nebraskan), drab to dark colored, starchlike fracture, few 



siliceous pebbles, leached 4 



2. Glacial till (Nebraskan) , oxidized, leached, about 1 



1. Glacial till (Nebraskan), oxidized, unleached, not well exposed, about. 40 



The summit of the hill is less than 20 feet lower than the Kansan gumbotil 

 plain, remnants of which are characteristic of this region. 



The bones were within the lower 10 feet of the Kansan till and only about 

 50 feet up the slope from the outcropping surface of the Nebraskan gumbotil. 

 The Kansan till is here oxidized, unleached, somewhat sandy, contains few 

 pebbles, and has some inclusions of the Nebraskan gumbotil. The bones all 



YI— Bull. Geul. Soc. Am., Vol. .32, 1020 



