376 A MANUAL OF DENTAL ANATOMY. 



animal, and to show the great development of the processes 

 for the attachment of muscles, and the stout wide arch of 

 the zygoma. 



To a particular tooth in the upper jaw, and to its antago- 

 nist in the lower jaw, Cuvier gave the name of " carnassial ;" 

 these, conspicuous in the true flesh-feeders, become less dif- 

 ferentiated in the Arctoidea or bear-like Carnivora, and in 

 the bears themselves are indistinguishable from the other 

 teeth, save by a determination of their homologies by a 

 process of comparison with the teeth of intermediate forms. 



The sectorial or carnassial tooth in the upper jaw is 

 always the fourth premolar ; its crown is divisible into two 

 parts, the one a thin sharp-edged blade, which runs in an 

 antero-posterior direction, and is more or less divided by one 

 or two notches into a corresponding number of cusps ; the 

 other part, the "tubercle," is a shorter and blunter cusp, 

 situated to the inner side of the anterior end of the blade 

 (see fig. 166). In those which are most purely flesh-feeders, 

 the " blade " is well developed, and the tubercle of small 

 size ; an increase in the tubercular character of the tooth is 

 traceable through those genera which are mixed feeders. 



The lower tooth which antagonises the upper carnassial, 

 passing a little behind it, is the first true molar; in the 

 Felidce it consists solely of the blade, which is divided into 

 two large cusps, behind which is a very small and rudimen- 

 tary third division (which in the Hycenidce, for example, is 

 of conspicuous dimensions). In existing Carnivora but one 

 " sectorial " tooth is to be found on each side of the jaws, but 

 in the Hysenodon and some other extinct tertiary mammals 

 there were three teeth partaking of this character. 



In a general sense we may say that the characters which 

 indicate a pure flesh diet are : the small size of the incisors 

 as compared with the canines, and their arrangement in a 

 straight line across the jaw ; the large size, deep implanta- 

 tion, and wide separation from one another of the canines ; 



