372 THE VERTEBRATE SKELETON. 



Order 9. PRIMATES. 



The dentition is diphyodont and heterodont, the incisors 

 generally number f , and the molars, except in the Hapalidae 

 (Marmosets), are f . The cheek teeth are adapted for grind- 

 ing, and the molars are more complex than the premolars. 

 A process from the jugal meets the postorbital process of the 

 frontal completing the postorbital bar. 



The clavicle is well developed, and the radius and ulna 

 are never united. The scaphoid and lunar of the carpus, 

 and commonly also the centrale, remain distinct from one 

 another. As a rule both manus and pes have five, digits, 

 but the pollex may be vestigial. The pollex is opposable to 

 the other digits, and so is the hallux except in Man; the 

 digits are almost always provided with flat nails. The hu- 

 merus has no ent-epicondylar foramen and the femur has no 

 third trochanter. 



The order Primates is divisible into two suborders : 



Suborder (1). LEMUROIDEA. 



The skull has the orbit communicating freely with the 

 temporal fossa beneath the postorbital bar (except in Tar- 

 sius}. The lachrymal foramen is external to the margin of 

 the orbit. Both pollex and hallux are well developed. In 

 the pes the second digit is terminated by a long pointed claw, 

 and so is also the third in Tarsius. The lumbar region of 

 the vertebral column is long, sometimes including as many as 

 nine vertebrae. Besides the Lemurs the group includes the 

 aberrant Tarsius and Chiromys. 



Suborder (2). ANTHROPOIDEA. 



The skull has the orbit almost completely shut off from 

 the temporal fossa, and the lachrymal foramen is situated 

 within the orbit. The pollex is sometimes vestigial or absent. 



