614 UNGULATES. 



and first discovered species of Mastodon, which Cuvier has termed 

 Mastodon giganteus and Mastodon angustidens. Fossil remains of 

 Proboscidians have subsequently been found, principally in the 

 tertiary deposits of tropical 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 estabhsh 

 transitional characters between the lamello-tuberculate teeth of the 

 Elephants, and the mammillated molars of the typical Masto- 

 dons ;(1) 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 qua- 

 drupeds. 



All Mastodons differ from the Dinotheres and resemble the 

 Elephants in the presence of two large tusks in the intermaxillary 

 bones. But those Mastodons with the more simple and typical 

 molar teeth likewise manifest the Dinotherian character in having 

 tusks in the lower jaw in the male : these are largest in the European 

 species (M angustidens, PI. 90, fig. 6, 'i) : they appear to have 

 been present in the young of both sexes, and are shown in the 

 immature jaw of the North American species {Mastodon giganteus) 

 in PL 144, fig. 13, d i ;{2) but it would appear from the examples 



(1) Mr. Clift had foreseen the possibility of the discovery of such a link, since supplied by 

 the praiseworthy exertions of Captain Cautley and Dr. Falconer, in his description of the 

 Fossil Remains from Ava, in the Geological Transactions, second series, vol. ii. " It is not 

 impossible," he says, " that there may yet be a link wanting, which might be supplied by an 

 animal having a tooth composed of a greater number of denticles, increasing in depth, and 

 having the rudiments of crusta petrosa, that necessary ingredient in the tooth of the Elephant : 

 the entire absence of which distinguishes the tooth of the Mastodon." Cuvier had previously 

 enunciated the same supposed distinctive character between the structure of the teeth of the 

 Elephant and Mastodon. "Dans I'elephant ces vallons sont enlierement combles par k cortical, 

 tandis que dans le Mastodonte ils ne sont remplis de rien." Ossemens Fossiles, torn, i., 4to. 

 1821, p. 225. The truth is, that the exterior of the fangs in all Mastodons is covered by a 

 moderately thick coat of cement (cortical of Cu\'ier, crusta petrosa of Clift) ; and that this sub- 

 stance extends upon the enamel of the crown, in a very thin layer, requiring microscopical 

 sections and examination in the typical Mastodons ; but augmenting in thickness in the £le- 

 phantoid and other species, with thinner and more numerous transverse divisions of the 

 crown of the grinders. 



(2) First described and figured by Dr. Godman, as indicative of a new genus, under the 

 name of Tetracaulodon, in the "Transactions of the American Philosophical Society," New 

 Series, Vol. iii, 1830, pp. 478—485, Pis. 17 and IS. 



