30 PACHYDERMATA. 



Cuvier has termed Mastodon giganteus and Mastodon angusti- 

 dens. Fossil remains of Proboscidians have subsequently been 

 discovered, principally in the tertiary deposits of Asia, in which 

 the number and depth of the clefts of the crown of the molar 

 teeth, and the thickness of the intervening cement are so much 

 increased, as to establish transitional characters between the 

 lamello-tuberculate teeth of Elephants, and the mammillated 

 molars of the typical Mastodons ; showing that the characters 

 deducible from the molar teeth are rather the distinguishing marks 

 of species than of genera, in the gigantic proboscidian family of 

 mammalian quadrupeds. 



" Two dental characters, however, exist, though hitherto, I 

 believe, unnoticed as such, which distinguish, in a well-marked and 

 unequivocal manner, the genus Mastodon, from the genus Elephas. 

 The first is the presence of two tusks in the lower jaw of both 

 sexes of the Mastodon, one or both of which are retained in the 

 male, and acquire a sufficiently conspicuous size, although small in 

 proportion to the upper tusks, while both are early shed in the 

 female. The second character is equally decisive ; it is the dis- 

 placement of the first and second molars in the vertical direction, 

 by a tooth of a simpler form than the second, a true dent de rem- 

 placement, 1 developed above the deciduous teeth, in the upper, 

 and below them in the under jaw. 



" These two dental characters, which are of greater importance 

 than many accepted by modern zoologists as sufficient demarka- 

 tions of existing groups of mammalia, have been recognised in the 

 species called Mastodon giganteus, most common in North 

 America, and in the Mastodon angustidens, which is the prevail- 

 ing species of Europe." 



But the value of these alleged characters, as furnishing certain 

 distinguishing marks between Mastodon and Elephant, is far from 

 being absolute. It will be seen in the sequel that premolars, 



1 ' British Foss. Mammal.' p. 273-4, and repeated in the ' Odontography/ p. 615. 

 These characters were not overlooked by Bronn : the inferior tusks are included in his 

 dental formula of Mastodon; and the displacement of the anterior grinder by a vertical 

 successor is also adverted to. 



