1 144 THE UNGULATES, OR HOOFED MAMMALS 



Another peculiarity of some, although by no means all mastodons, is the presence 

 of a pair of larger or smaller tusks in the lower as well as in the upper jaw; the ex 

 tremity of the lower jaw in such species being prolonged into a spout-like projection 



' There are a larger number of species of mastodons, ranging over a great part 

 Europe Southeastern Asia, and the whole of America; the earliest representatives 

 of the group occurring in Europe in the middle division of the Miocene period. _ And 

 it is noteworthy that all these earlier species had but three transverse ridges m t. 

 third fourth and fifth molar teeth, thus approximating the closest to other Ungul 



THE LAST LEFT UPPER MOLAR TEETH OF TWO SPECIES OF INDIAN MASTODONS. 



The upper figure (two-thirds natural size) belongs to M. latidens, and the lower (one-half 

 natural size) to M. cautleyi. In the specimen represented in the upper figure the 

 first two ridges are partially worn, while in the lower one they are intact. 



One of the best-known species is the North- American mastodon (Mastodon 

 americanus) , of which teeth and bones, and sometimes entire skeletons, are found in 

 enormous quantities in the peat and lacustrine deposits of Ohio and Missouri. This 

 animal had enormous tusks in the upper jaw, but either none or mere rudiments in 

 the lower jaw; and its molar teeth, with the exception of the last, had only three 

 ridges, in which the longitudinal cleft was but slightly marked. Some of the teeth 

 are so fresh looking as to appear almost like those of recent elephants, and it seems 



