MASTODON. 385 



ture of the lower jaw, to the huge bilophodont Mammal, first 

 made known by Cuvier under the name of " Tapir gigan- 

 tesque." The length of the skull, from f to d, in fig. 138, is 3 

 feet 8 inches. The teeth in this skull, in addition to the two 

 large deflected tusks of the lower jaw, are five in number on 

 each side of both jaws. A study of the changes of dentition 

 in fossils of young Dinotheria shew that the first two teeth 

 answer to the third and fourth premolars, as signified by the 

 symbols p, 3 and 4; and that the rest are true molars (m, 

 1, *, 3). Of these, the first tooth (p, 3), is rather trenchant 

 than triturant ; the third tooth (1) has three transverse 

 ridges. The other grinders have two transverse ridges. This 

 "bilophodont" or two-ridged type is shewn by the molars 

 of the Tapir (fig. 139), Lopliiodon, Megatherium, Diproiodon, 

 Nototherium, Kangaroo, and 

 Manatee. In the general shape 



m%\% u-m 



of the skull and aspect of the 



nostrils Dinothcrium most re- P 



Fig. 139. 



sembles Manatus ; but bones „. . . _ . 



Molar series, lower jaw. lapir. 



of limbs have been found so 



associated with teeth as to determine the Dinothcrium to be a 

 hoofed quadruped, of probably aquatic habits, and transitional, 

 as it would seem, between the large Lophiodons and the huger 

 proboscidians. The evidences of the genus have been dis- 

 covered in miocene deposits of Germany, France, Switzer- 

 land, and Perim Island, Gulf of Cambay. 



Genus Mastodon, Guv, — The earliest appearance of this 

 genus of proboscidian or elephantoid Mammal is in tertiary 

 strata of miocene age, and by a species in which the fore part 

 of the lower jaw was produced into a pair of deep sockets 

 containing tusks ; but these are only slightly deflected from 

 the line of the grinding teeth (fig. 140, C). This species of 

 Mastodon, discovered in the miocene of Eppelsheim, was called 

 longirostris by Kaup ; but he afterwards recognized it as the 



2c 



