472 ZOOLOGY SECT. 



pletely opposable to the other digits. There are nearly always 

 five digits, provided with flat nails in both manus and pes. The 

 orbit is surrounded by a complete bony rim. The clavicles are 

 in all cases well developed. There is no foramen above the inner 

 condyle of the humerus, and the femur rarely has a third trochanter. 

 The stomach is generally simple. The testes descend into a 

 scrotum. There are nearly always two teats on the thoracic region. 

 The placenta may be non-deciduate, or deciduate and meta- 

 discoidal. 



Sub-order a. Prosimii. 



Ape-like, mostly nocturnal, arboreal Primates of comparatively 

 low organisation. All the digits of both feet are provided with 

 flat nails, except the second of the hind-foot, which has a claw. 

 Both the pollex and hallux are always well developed. The 

 posterior, bony rim of the orbit is a narrow bar beneath which 

 there is a free communication between the orbit and the temporal 

 fossa. The lacrymal foramen is situated outside the margin of the 

 orbit. In nearly all cases the inner pairs of incisors of the upper 

 jaw are separated by a median space. The cerebral hemispheres 

 are not very highly developed, and do not completely overlap 

 the cerebellum. There may be an additional pair of teats on the 

 abdomen. The uterus is two-horned and the placenta diffuse. 



This sub-order comprises the Lemurs (Lemur, Tarsius, and other 

 genera) and Aye- Ayes (Chiromys). 



Sub-order b. Anthropoidea. 



Most highly organised Primates, chiefly modified for an arboreal 

 life. The digits are all provided with flat nails, except in the 

 Hapalidse, in which all except the hallux are provided with a claw. 

 The pollex is in some rudimentary or absent. The orbit is separated 

 from the temporal fossa by a broad vertical plate, and the lacrymal 

 foramen is situated within the margin of the orbit. The inner upper 

 incisors are in close contact. The cerebral hemispheres are usually 

 richly convoluted, and completely, or nearly completely, cover over 

 the cerebellum. The uterus has no horns. The placenta is deciduate 

 and metadiscoidal. 



Family i. Hapalidce. 



Anthropoidea with the pollex not opposable, all the digits except 

 the hallux provided with curved pointed claws, without cheek- 

 pouches or ischial callosities, with a broad nasal septum, without 

 bony external auditory meatus, and with a non-prehensile tail. 



O 1 Q O 



The dental formula (vide p. 545) is i. ^ c. ,, p. ~, m. ^ = ^2. 

 This family includes the Marmosets (Hapale). 



