i go ALLEN'S NATURALIST'S LIBRARY. 



in the male (less so in the female) for the reception of the 

 vocal apparatus. Their incisor teeth are small and equal, the 

 canines are prominent and have an oblique ridge across the 

 crown from the outer front, to the inner hind, cusp, and the 

 upper molars are large. The tail is powerful and prehensile, 

 naked towards the tip, where it is tactile and very sensitive. 

 The thumb is movable, the face is naked, and the chin 

 bearded. Some have short, and some have long, fur over their 

 bodies, but it is generally more plentiful about the head. In 

 appearance they are the most unattractive and repulsive of 

 the American Monkeys. Their intelligence is also of a very 

 low order. 



The roof of the brain-case is depressed ; the plane of the 

 opening for the passage of the spinal-cord from the brain is 

 almost perpendicular to that of the base of the skull; the 

 condyles for the articulation of the neck are situated as far 

 back as possible. Sir William Flower, in his valuable mono- 

 graph on the brain of Mycetes, has shown that the frontal lobes 

 are small and the cerebral hemispheres only just cover the 

 cerebellum. In regard to its grooves and convolutions, the main 

 brain (cerebniJii) of Mycetes can be distinguished from that of 

 all other Monkeys. The whole organ is small as compared with 

 the size of the animal ; it wants the roundness and fulness 

 of that of the Spider-Monkeys (Ateles) and of the Capuchins 

 (Cebus). Its surface markings are comparatively few and 

 simple, and depart remarkably from the ordinary type seen in 

 the order. In the Old World Apes there is a striking simi- 

 larity in the character of the surface markings of their cerebral 

 hemispheres. There is a slight ascensive development from 

 Cercopithecus towards Hylobates ; and further complications 

 overlying the same primitive type such as large proportionate 



