THE PRIMATES EXCEPT MAN 



119 



Alouatta is also a specialized type although the hinder mar- 

 gin of the palate in this animal has traveled backward. The 

 mandible presents a striking feature in the enormous expan- 

 sion of the body at its junction with the ramus. There is also 

 considerable restriction of the interdental space as far back 

 as the first molar by the deposit of bone on the inner aspect 

 of the jaw. The small incisors, both upper and loAver, slope 

 forward as in Ateleus. The canines are large. The premolars 



Fig. 40. — Dentition of Howler (Alouatta palliata, Gray; 9.822-1). The cres- 

 cent-cusped molars of this dentition should be compared with those of Lichanotus 

 (Fig. 37). The upper incisor and canine series is imperfect in this specimen. 



are bicuspid and in the mandible the first is larger than either 

 of the other two. In the upper molars which slightly decrease 

 in size from the first backward, the pronounced character of the 

 external cingulum and the development of a mesostyle combine 

 to provide the teeth with crescendo cusps concave oivhvard 

 like those of the marsupial Koala. It will be recalled that the 

 diet of the Koala consists almost wholly of leaves. A 

 resemblance between the lower molars of these two animals is 



