82 PROCEEDINGS OF THE CHICAGO MEETING 



lay within 10 feet of the surface of the slope below which the road has been 

 cut, and yet the evidence is clear that the bones became included in the till 

 during the Kansan Glacial epoch and not since the development of the slope 

 by erosional agencies. 



The tusk which was found when the road was being graded was measured 

 by Mr. Cox, who reports that it was 9 feet 7 inches long. The bones which 

 were discovered later by excavation were about 10 feet distant from the first 

 tusk. These bones were closely related one to the other ; a shoulder-blade lay 

 flat and end to end with a bone which from the description of Mr. Stubbs was 

 probably a humerus; a tusk overlay the shoulder blade, and the other frag- 

 ments were closely associated with these bones and in the same plane. The 

 tusk which was lying on the shoulder-blade was measured by Mr. Stubbs, who 

 found it to be 11 feet 4 inches long. This length was verified by a measure- 

 ment of the mold of the tusk which was still distinct in the drift at the time 

 of our examination. The mold in which the tusk lay showed no evidence of 

 fracture, flattening, or other distortion. This tusk was curved in two planes; 

 apparently when in position in its socket it curved downward and outward, 

 then upward to the tip. 



The tusks when exposed to the air crumbled into a white powdery substance. 

 Pieces of only a few inches in diameter were seen intact, and these showed 

 the concentric structure of ivorj-. The bones were so fragile that they crum- 

 bled at the touch ; no pieces showed any sort of hardening. All the bones 

 maintained their shape and were of a grayish white color. Although impreg- 

 nated with soil the cancellated structure was distinct. A spade or pick passed 

 through the bone as readily as if it were soft clay. 



Significance of the Relationships of the Fossils 



The tusks and limb bones were found in the base of Kansan till which over- 

 lies Nebraskan gumbotil. The characteristics of the tusks and bones and their 

 relationships indicate fairly conclusively that they were parts of a single 

 animal, the remains of w^hich were lying on the surface of the Nebraskan 

 gumbotil when they were picked up by the advancing Kansan ice, and that 

 while they were being transported a short distance they became imbedded in 

 the base of the Kansan till. The relation of the remains to the surface of the 

 Nebraskan gumbotil, which is perhaps the most distinctive Aftonian inter- 

 glacial horizon-marker which has yet been found, suggests strongly that the 

 mammoth or mastodon had been living near the front of the Kansan ice-sheet 

 during the Kansan Glacial epoch. If this interpretation is correct, then the 

 habitat and the age of the mammoth or mastodon are here indicated more 

 definitely than in many other places in Iowa where similar remains have been 

 found in gravels. These gravels have been interpreted to be Aftonian inter- 

 glacial gravels, related neither to the melting of the Nebraskan ice-sheet nor 

 to the advance of the Kansan ice-sheet. In this connection it is of interest to 

 state that recent study by the writer of many of the gravels in which pro- 

 boscidean and other remains have been found suggests that at least some of 

 the gravels are not distinctive interglacial deposits separating the two oldest 

 drifts, the Nebraskan drift and the Kansan drift, but are lenses and irregu- 

 larly shaped masses of gravels incorporated in till and related closely in age 



