556 
UNGULATES. 
The Mastodons. 
Genus Mastodon. 
The above-mentioned stegodont elephants so closely connect the genus Elejdias 
with the extinct animals known as mastodons, that the division between the two 
genera is a somewhat arbitrary one. It is noteworthy that the species of mastodon 
most nearly related to the stegodont elephants are found in the same regions as 
THE LAST LEFT UPPER MOLAR TEETH OF TWO SPECIES OF INDIAN MASTODONS. 
The upper figure (§ nat. size) belongs to M. latidens-, and the lower (£ nat. 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. 
the latter, from which we may infer that the evolution of the elephants from the 
mastodons took place in South-Eastern Asia. 
Mastodons are distinguished by their molar teeth, as shown in the accompanying 
figure and the one on p. 557, having comparatively few transverse ridges, which 
are low, and more or less completely divided by a longitudinal cleft into inner and 
outer columns. These ridges are separated by valleys in which there is little or 
no cement; and when worn down by use they exhibit more or less trefoil-shaped 
surfaces of ivory, quite different from the elongated ellipses formed in those of the 
