A MEANS OF ESTIMATING THE AGE OF THE MAS- 

 TODON AND OTHER PllOBOSCIDEA 



(Abstkact) 

 HENRY FAIRFIELD OSBORN 



The skeleton known as the Warren Mastodon, discovered in 

 Newhurgli, N. Y., in 1845, and monographed by John ColHns 

 Warren, has been remounted recently in the American Museum of 



Fig. 1. 



Natural History. In repairing the tusks, the outer sheathing of the 

 dentine was found in large part absent. The inner sheathing exposed 

 a series of concentric constrictions and expansions which were observed 

 to be approximately symmetrical on the two sides, as indicated by 

 the series of + signs in Fig. 3, A and B. Secondly, it was noted that 

 the intervals between these constrictions are broader in the middle 

 and fore part of the tusks (corresponding with the youthful stage of 

 growth of the tusk) and become narrower toward the base of the 

 tusk (corresponding with the mature or adult stages of growth). 

 Eighteen of these rings are preserved on one side and thirteen on the 



