HAPALIDM. 729 



temporal fossa by a bony partition ; the lachrymal foramen is situated 

 within the margin of the orbit ; the median upper incisors are in 

 contact ; the cerebral hemispheres are richly convoluted, and hide or 

 almost cover the cerebellum ; the transverse portion of the colon 

 extends uninterruptedly across the abdomen ; the mammse are never 

 abdominal ; the uterus is not bicornuate but simple ; the placentation is 

 meta-discoidal. 



Family i. Hapalid^e ( = Arctopithecini). Marmosets. 



The marmosets are the smallest monkeys, not much larger 

 than squirrels. They live in companies in the Neotropical 

 forests, especially in Brazil, and feed on insects and fruit. 



Their dentition |p| is distinctive, for other Anthropoidea 

 have - 3 molars. There is a broad septum between the 

 nostrils, as in the other New World monkeys ; the external 

 auditory meatus is not bony. The parietal and jugal are 

 in contact. The tail is long, hairy, and non-prehensile. 

 The arms are not longer than the legs ; there are no cheek 

 pouches nor ischial callosities. The thumb or pollex is 

 long, but not opposable ; all the digits have a pointed claw 

 except the great toe or hallux, which is very small. The 

 marmosets often bear three young ones at a birth, whereas 

 the other monkeys usually bear but one. There are two 

 genera, Hapale and Midas. 



Family 2. Cebid^e ( = Platyrrhini). American Monkeys. 



In the American monkeys the nose is flat, with a broad 

 internarial septum. They occur throughout tropical 

 America, but are most at home in Brazil. All are arboreal, 

 and many have prehensile tails. The digits have nails, not 

 claws; the thumb is somewhat opposable, and divergent 

 from the fingers, except in the spider monkey — Ateles — in 

 which it is rudimentary. The skull is rounded, and the 

 frontals form a V-shaped suture with the parietals. The 

 external auditory meatus is not bony. The parietal and 

 jugal are in contact, separating the frontal from the ali- 

 sphenoid. The dentition is characteristic, for there are six 

 back teeth; the formula being 2133. 



Examples. — The howling monkeys {Mycetes), with large vocal 

 organs protected by the expanded mandibles, and with an 



