620 UNGULATES. 



fangs, the anterior and smaller one supporting the anterior pair 

 of cusps, the posterior the remainder of the crown. 



The vertically succeeding tooth of the second molar (ib. ^1) 

 follows the usual law in having a less complicated crown than the 

 tooth which it replaces : it has only two pairs of principal cusps, 

 and is a sort of magnified representative of the first small deci- 

 duous molar, which has no successional tooth. (1) The external 

 and anterior cusp is the longest, the base of the crown is partially 

 surrounded by a tuberculate ridge. This tooth, when fully deve- 

 loped, has three roots, of which the outer and anterior one 

 supports the corresponding cusp ; the other two supporting the 

 rest of the crown. Specimens have been found in which all the 

 four cusps have been worn down to their base; but the insular 

 patches of dentine have been distinct and severally surrounded by 

 their thick enamel. 



The fourth molar, (2) in the order of size, is anterior to the 

 preceding in the order of development, and is the third in the order 

 of position (ib. fig. 12, c^ 3) before the fall of the two deciduous teeth, 

 and the second after the acquisition of the vertically succeeding molar. 

 I regard it as being essentially the last of the true deciduous 

 series, but which has no vertical successor. The grinding surface 

 presents four pairs of cusps and a small posterior ridge or talon : (3) 

 the first pair of cusps is the smallest and is most complicated with 

 accessory tubercles : the bases of the cusps encroach reciprocally 

 upon each other's interspaces across the middle longitudinal valley, 



(1) If the premolar (p 1) succeeded the first small molar, as described by Dr. Kaup, (Sur le 

 Mastodon longirostris, 4to. 1835, p. 70.) it would form an exception to the rule; hut the spe- 

 cimen of the upper jaw of Mastodon angustidens from Dax figured by Cuvier, Ossera. Fossiles, 

 Divers Mastodontes, PI. iii, fig. 2, shows the unworn cusps of the quadri-cuspid successional 

 molar projecting into the socket, whence the sex-cuspid deciduous tooth has been extruded. 

 Cuvier figures one of these teeth, from Dax, loc. cit., PI. 1, fig. 2, in which the two anterior 

 cusps are blended into a single irregular surface ; behind which are the worn tips of the 

 posterior pair of cusps. 



2) Kaup, ib. PI. XVI, fig. 1 & 1 o ,• PL xx, fig. 2 ; PI. xvii, fig. 13 & 14. 



(3) This tooth is described in my * History of British Fossil Mammalia,' p. 286, as having 

 three pairs of mastoid tubercles and ' a large posterior tuberculate talon', two of the tubercles in 

 that talon (fig. 100, p. 284) corresponding with the fourth pair, here described. The two 

 extremes in the varieties of the talon in this tooth may be seen in Cuvier's ' Divers Mastodons* 

 PI. iii, fig. 2, and Kaup's PI. xvi, fig. 1 & la, and I have, as yet, no evidence that they charac- 

 terize distinct species. The English fossil (fig. 100, ' Br. Foss. Mam.') is an intermediate varie^ 



