CARNIVOKA. 



419 



may be distinguished tlie part called the " blade " (fig. 1 62, 

 h, &), and the part called the "tubercle" (t). The lower 

 sectorial in the genus Felts consists exclusively of the blade 

 (fig. 163), which is pretty equally 

 divided into two lobes. The blade of 

 the upper sectorial always plays upon 

 the outside, and a little in advance, of 

 the lower sectorial. 



The upper sectorial succeeds and 

 displaces a deciduous tubercular molar 

 in all Carnivora, and is, therefore, essen- 

 tially a premolar tooth ; the lower sec- 

 torial comes up behind the deciduous 

 series and has no immediate predeces- 



sor; it is, therefore, a true molar, and 



Fig. 163. 



the first of that class. The sectorial Side view of lower sectorial 



. . tooth, Lion. Nat. size. 



teeth present gradational varieties of 



form in the carnivorous series, from Machairodus, in which the 

 crown consists exclusively of the "blade" in both jaws, to 

 Ursus (fig. 164, m i), in which it is totally tubercular; the 



Fig. 164. 



Dentition of the Bear (Ursus). 



development of the tubercle bearing an inverse relation to the 

 carnivorous propensities of the species. 



