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.—Hominidee.—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 343§, 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 
