MAMMALIA. 



591 



The two families of Old World monkeys differ so markedly from 

 the two New World families that there is great probability of their 

 having been independently evolved. The chief differences are as 

 follows— In the skull the New World monkeys always have three pre- 

 molars and three or two (marmosets) molars, an auditory bulla with no 

 bony auditory meatus ; the alisphenoid is suturally united with the 

 parietal to the exclusion of the squamosal from the frontal. In the Old 

 World monkeys there are always only two premolars and three molars, 

 there is no auditory bulla, but there is a bony auditory meatus and the 

 squamosal has a sutural connection with the frontal. 



Fig. 397.^— Bones of the Ankle and Foot of Gorilla. 



Note the opposable hallux and shortness of the " instep." 



Family 5. — Hominidae. — Man is now usually regarded as forming a 

 zoological family of the Primates. He differs anatomically from the 

 other families in the very high development of the brain, in the great 

 proportionate length of the hind-limbs, the non-opposable hallux, the 

 curvature of the spine and other minor features correlated with an 

 upright gait. His dentition is IHf , but differs from that of all monkeys 

 in having an even series of teeth with no diastema. 



Distribution of the Anthropoidea, — The occurrence of 

 two differing series of monkeys in the Old and New World 



