44 THE MAMMALIAN ORDER PRIMATES [SECT. A 



Neanderthal skeleton and its congeners probably represent forms specifically 

 distinct from Homo sapiens. The fuller consideration of these extinct types 

 is reserved however for a later chapter (xvn). 



It is now convenient to enumerate the diagnostic characters of 

 the various Sub-orders of the Primates. For this purpose, the 

 concise statements made by Professors Parker and Haswell (in 

 their Textbook of Zoology) have been drawn on freely (with 

 permission). 



Order Primates : Eutheria, nearly all of which are adapted 

 to an arboreal life, the limbs being prehensile owing to the pollex 

 and hallux being more or less completely opposable to the other 

 digits. 



Dentition : heterodont ; diphyodont ; incisor teeth two in 

 number on each side above and below : the Aye-Aye (Cheiromys) 

 and Tarsii are exceptions to this rule. 



Digits : are, in nearly all, five in number, and are provided 

 with flat nails both in manus and pes : the pollex and hallux 

 are opposable. 



Forearm : the ulna and radius are separate {i.e. not ankylosed 

 as in many Eutheria) and well developed. 



Orbit : surrounded by a bony ring. 



Clavicles : well developed. 



Entepicondylar foramen : abnormal (Parker and Haswell say 

 absent). 



Third trochanter of femur : abnormal (Parker and Haswell 

 say absent). 



Stomach : simple in most instances. 



Testes : descend into a scrotum. 



Mammae : usually two in number, and thoracic in position. 



Placenta : variable (diffuse or meta-discoidal). 



SUB-ORDER 

 LEMUROIDEA 



Ape-like Primates, nocturnal in habit, and of comparatively low 

 organisation. (Cf. Fig. 17.) 



Teeth: dental formula i, f; c, \; pm, f; m, f; the upper 

 medial) incisor teeth are widely separated in most cases. 



