KINE TOGENESIS. 



337 



location in a particular part of the jaw. For it has 

 been already stated that in the evolution of the secto- 

 rial dentition of the Carnivora, the number of molars 

 and premolars has considerably diminished, while 

 those that remain have become relatively much larger. 

 In the tritubercular dentition the crowns proper of 

 one jaw alternate with those of the other (Fig. loo); 

 but when heels are added in either jaw, they will op- 

 pose such part of the crowns of the teeth in the oppo- 



Fig. 100. — Centetes ecaudatus: A^ skull, side seen obliquely from below; 

 B, superior molars from below ; C, inferior molars from above. 



site jaw as comes in contact with them when in use. 

 The development of the heel in the inferior molars 

 produced a type which is known as the tuberculosec- 

 torial. This type characterizes the Creodonta and a 

 few Carnivora. In the former there are generally 

 three such teeth, in the latter but one. 



In the tuberculosectorial type of inferior molar the 

 primitive tritubercular part of the crown (trigonid of 

 Osborn) stands principally anterior to the posterior 



