MYCETES SENICULUS 193 



capacities. In addition to this specialization, the howHng monkeys have 

 a sinus-like diverticulum in the larynx larger than that of any of the other 

 American monkeys. The hyoid bone is much enlarged and contains a cavern- 



CouTlesy, American Museum oj Natural History 



FIGS. 95 AND 96. TWO VIEWS OF MYCETES SENICULUS, THE RED HOWLING 

 MONKEY OF SOUTH AMERICA, SHOWING ITS PREHENSILE TAIL. 



ous dilatation, while the mandible, in order to protect the underlying struc- 

 tures, is likewise unusually large and heavy (Fig. 95). 



The howling monkeys also possess an opposable thumb and well- 

 developed toes. They are described as being the most ferocious of South 

 American monkeys, at the same time having the lowest degree of 

 intelligence. Their mournful howlings are often audible for miles around. 

 Their cries are supposed to be employed as a means of defense in order to 

 intimidate their enemies. Their vocal powers are so awe-inspiring that the 



