266 



ELEMENTARY ANATOMY. 



[LESS. 



forms but a single prism, and is therefore like half of one of 

 the teeth last described. Such a condition exists in Ceutetes^ 

 Hernicentetes, and especially in Chrysochloris. 



eHRYSOCHLORO 



FIG. 239. GRINDING SURFACES OF UPPER MOLARS OF LEFT SIDE. 

 a, b, and c, remnants of principal cusps. 



Another kind of modification of the teeth is that by which 

 the typically carnivorous molar is arrived at. This is best 

 exemplified by the last pre-molar, which in the Dogs, Cats, 

 and their allies has been called the "sectorial" or " carnassiai " 

 tooth of the upper jaw. 



FIG. 240. DENTITION OF THE SABRE-TOOTHED TIGER (MacJiairodns). 

 (TYPICAL CARNIVOROUS DENTITION.) 



Here (in the Cats) it consists almost entirely of three sharp, 

 strong, unequal cusps placed one behind the other on the outer 

 margin of the tooth, and connected together by trenchant 

 ridges, while inside the foremost cusp is a small, short, 

 and blunt accessory one. From a study of Marsupial teeth 

 it appears that the three outer cusps answer to the cusps of 

 the cingulum blended with the two outer principal cusps of 

 man, while the rudimentary internal cusp is the representative 



