724 MAMMALIA. 



2 



diphyodont and heterodont ; the incisors do not exceed - ^ 



3 2 



the molars are - except in the marmosets where they are - ; 



3 2^ 



the axis of the orbit is directed forward, and the orbit is 

 closed off from the temporal fossa ; the clavicles are well 

 developed ; the radius and ulna are never united ; the 

 scaphoid, the lunar, and usually the os centrale remain 

 distinct from one another ; there are usually five fingers and 

 five toes, but the thumb may be absent or rudimentary ; 

 the big toe is opposable except in man, and has a fiat nail 

 except in the orang ; the thumb is usually more or less 

 opposable ; the cerebral hemispheres have numerous con- 

 volutions and overlap the cerebellum ; the stomach is simple 

 except in Semnopithecus and its relatives, in which it is 

 sacculated, and there is a caecum which is often large ; 

 there are two mammse on the breast ; the uterus is simple ; 

 the testes lie in a scrotum ; the placenta is meta-discoidal, 

 being developed by the concentration of the villi from a 

 diffuse area into a well-defined disc. 



Some of the characteristics in which the Anthropoidea 

 differ from Lemuroidea may be re-emphasised : — the orbit is 

 separated from the tempioral 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 mamma; 

 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, being no larger 

 than squirrels. They live in companies in the Neotropical 

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



Their dentition ^'^' is distinctive, for other Anthropoidea 

 have - molars. There is a broad septum between the 



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

 auditory meatus is not bony. The tail is long, hairy, and 



