MASTODON TETRACAULODON. 137 



is fifty-eight inches ; the entire width of the latter is seventy-four. ; making Mastodon 



Tetracau- 



a difference, in the whole width, of sixteen inches, while the difference in i don. 

 the apertures of the pelves is much less. The aperture in the Cambridge 

 skeleton, in the transverse direction, -is nineteen inches ; in that of the 

 other, twenty-one ; making a difference of only two inches. 



There is also a remarkable disproportion between the tusks of the two 

 skeletons. The length of the tusk in the Cambridge skeleton is about 

 thirty-six inches ; and of the other, a hundred and twenty-six. The tusk 

 of the former is nearly straight, and that of the latter much curved. 



The comparison of the apertures of the pelves, and of the size of the 

 tusks in the two specimens, has led to the opinion, that one of these was 

 male, and the other female. In objection to this inference, it might be 

 suggested that one of these was the skeleton of a younger animal than the 

 other. The state of the teeth, however (which are the same in number and 

 form in both), makes it probable that the difference in age was not very 

 great ; and the condition of the epiphyses affords an additional though not 

 so strong a support to this hypothesis. A comparison of the other bones 

 has not afforded any important results tending either to strengthen or 

 weaken it. 



On the whole, it appears that there are no such differences in the jaws, 

 the teeth, or any other part of the bony skeleton, as would call on us to 

 separate the specimens "containing mandibular tusks from those which are 

 destitute of them. And we have no doubt that the acknowledged differences 

 depend on the difference of sex ; the Tetracaulodon being the male, and the 

 Xon-tetracaulodon the female, of the Mastodon Giganteus. 



18 



