THE PRIMATES. 619 



eries have led to the hypothesis, that from still older, more 

 generalized types, four lines of development, respectively 

 culminating in the typical Carnivores, Cetaceans, lemurs, and 

 monkeys, have taken their origin. That the lemurs, though 

 now restricted to Madagascar, eastern Asia, and South 

 Africa, were preceded by still more generalized types on the 

 American Continent, is indicated by the discovery of fossil 

 bones in the Eocene beds of the Rocky Mountains, referred 

 by Marsh and Cope to the Primates ; Marsh stating that 

 the principal parts of the skeleton are " much as in some of 

 the lemurs." 



Allied to the true lemurs is a very puzzling creature, the 

 aye-aye or Chiromys, of Madagascar, whose dentition differs 

 from that of all other Primates, and resembles that of the 

 Rodents ; the thumb also is not truly opposable, and all the 

 hind digits, except the great toes, have claw-like nails. The 

 Galago, of West Africa, somewhat recalls the Insectivora, 

 while " in the more active and flexible-bodied Lemuridce, 

 the trunk-vertebrae resemble in proportions, connections, and 

 direction of neural spines those of the agile Carnivora." 

 (Owen.) 



The genuine Primates or suborder AntJiropoidea are, in 

 brief, characterized by the large, convoluted cerebral hemi- 

 spheres which nearly, or in the higher apes and man, conceal 

 the cerebrum when seen from above. * The ears are rounded, 

 with a distinct lobule, and the two mammae are pectoral. 

 These AntJiropoidea are divided into two subdivisions, the 

 first comprising the monkeys and apes, and the second, man. 

 In the first group (Simice), the body is prone, the animal 

 walking on all-fours, only the orang and gorilla walking 

 partly erect ; the great toe is rather short, thumb-like, and 

 opposable to the fingers, while the body is very hairy. The 

 monkeys of the New World have a wide septum to the nose, 

 and are hence called Platyrhinw ; they also have long tails. 



The little, squirrel-like, gregarious marmosets are the small- 

 est of the monkeys and nearest allied to the lemurs. They 

 walk on all -fours, the anterior extremities being like the 



*In the low Hapcde and Cebus, however, the cerebrum projects 

 backward as far or even farther than in man (Gill). 



