xxiv INTRODUCTION 



it is not sacculated, and when fully distended with air is curved on 

 itself into little less than a circle ; it is furnished with a well developed 

 median f renum carrying blood vessels." 



The last genus is Saimiri having eight species. These are small 

 active animals with large eyes, and the occipital region of the skull 

 projected posteriorly. 



The third Subfamily is Aotin^e with a single genus Aotus con- 

 taining fourteen species. These are eminently nocturnal animals, of 

 small size, and with large eyes placed close together. The fourth Sub- 

 family is Cebin^e with four genera; the first Ateleus, generally 

 known as 'Spider Monkeys,' on account of their slender bodies 

 and long limbs, with twelve species. The pollux is usually absent, and 

 the tail prehensile, the animals of this genus being so expert in the use 

 of this organ as to make it perform the service of an extra hand. The 

 next genus is Brachyteleus with only one species ; a long limbed, 

 heavy bodied creature, with, like Ateleus, the thumb usually wanting. 

 It is closely allied to the 'Spider Monkeys.' The third genus is Lago- 

 thrix having six species. Unlike the members of the two previous 

 genera, the species of this one have a well developed thumb. The body 

 is heavy, the round head covered thickly with short hairs, and best 

 described as 'bullet-headed.' The animals are slow in movement, of a 

 gentle disposition, and a delicate constitution. The fourth genus 

 being the last of the American Monkeys is Cebus with twenty-two 

 species and two subspecies. On account of the great variability in the 

 coloring assumed by individuals, the members of this genus are the 

 most difficult to determine of the Primates. They also, by certain of 

 the species, are most generally known of all Monkeys. The face is 

 flat, the muzzle not protruding. The brain has numerous convolutions, 

 and the animals are intelligent, vivacious and very mischievous. 



The Apes, Baboons and Monkeys of the Old World comprise the 

 Cratarrhine section of the Primates, or those with, among other 

 characters, the nostrils directed downward. There are only three 

 Families and two Subfamilies possessing, altogether, twenty-two 

 genera. The first Family is Lasiopygid.e with eleven genera. Papio, 

 the first genus, has nineteen species including the dog-faced baboons, 

 so called on account of their long muzzle. These are large, powerful 

 animals, associating in herds, commanded by one or more patriarchal 

 members, and are formidable antagonists when attacked. Thero- 

 pithecus contains but two species, large in size and heavily maned, in 

 this respect allies of Papio hamadryas. The third genus is Cyno- 

 pithecus the black Apes of Celebes ; peculiar looking animals without 



