178 COMPABATIVE DEHTAL ANATOMY 



. 2-2 1-1 ^ w 3-3 m 3-3 o R 

 '• 2=2 C ' 1=1 P ' m - 3=3 m * 3=3 = 36 ' 



The Halpiadae have but thirty-two teeth. The 

 presence of the third premolar in this branch, 

 along with other peculiarities, indicates that they 

 are nearer the Lemurs than the Old World Pri- 

 mates, and are therefore lower in structure. 

 They have stopped at a lower stage of develop- 

 ment, and the Old World branch has progressed. 

 The Catyrrhine, the Old World Monkeys, and 

 Apes have the formula, — 



. 2-2 1-1 2-2 3-3 QO 



i. ^ c. — p.m. — m. _ = 32, 



which is exactly that of man. There is one less 

 premolar on each side of each jaw than in the 

 New World Monkeys. However, of the latter, the 

 little Marmoset has only thirty-two teeth, owing 

 to the absence of the third molar on each side, 

 although they still have the third premolar. The 

 Platyrrhines have the third molar in the decidu- 

 ous set also. Some of the species have nearly 

 horizontal incisors, — another lingering lemurine 

 characteristic, — but the teeth as a rule begin to 

 approach the erect position. The incisors are 

 thick and strong, and of nearly the same width. 

 The canines are strong and prominent, and ap- 

 pear before the last molars. The diastemas in 

 front are well marked, into which the lower ca- 

 nines close, as in the carnivora. The molars 



