SKULL MAMMALS 



219 



Primates (sens, lat.)- — The primate skull has a wide range of form from the 

 lowest Lemuroid to man. The facial parts in the lowest genera recall those of 

 .Carnivores, and the brain cavity is as small relatively as in that group. In the 

 highest genera the increase in size of the brain increases the posterior part of the 

 skull so that the face is less prominent. All Primates have an complete zygoma 

 and the orbit is separated from the temporal fossa by a postorbital bar, the 

 separation being so complete in apes and man that only a narrow cleft remains 

 between bar and the rest of the cranium. The orbits themselves are directed 

 more or less forwards. Some genera have a sagittal crest, others have none. 

 The position of the occiput also varies, being nearly vertical in the lower, nearly 

 horizontal in the higher groups, there being a few exceptions to both statements. 

 Ali- and orbitosphenoids fuse with basi- and presphenoid respectively, forming 

 the alfe magna; and parvae of human anatomy; and often fusion of basi- and 

 presphenoids results in a single sphenoid bone. 



ProsimiiE (Lemuroidea) usually have the facial part of the cranium elongate, 

 a sagittal crest of varying size, and frequently an interparietal. The orbit is 



Fig. 231. — Skulls of (.4) Tarsius (Gregory, '20), and (S) adult orang-utan (Wiedersheim, 



'08). 



largely bounded by zygomatic and frontal, lacrimal and ethmoid being less 

 prominent. The orbit is connected with the temporal fossa beneath the post- 

 orbital bar. The zygomatic arch is usually slender, the zygomatic bone not 

 reaching the shallow mandibular fossa which often has a postglenoid process. 

 The lacrimal foramen may be in the bone or between it and the maxilla. The 

 alisphenoid reaches the frontal and lacks a foramen rotundum. An optic 

 foramen is present. The small premaxillae reach the nasals. The hard palate 

 is long. The halves of the lower jaw are rarely fused at the symphysis, the ramus 

 is high and the condyle rounded. 



Tarsius (fig. 231, .4) needs special mention, since, while Lemurine in general 

 make-up, it is Hke man in many cranial features and consequently has received 

 much attention. Among these points are the short facial region, the small cleft 

 beneath the postocular bar, no sagittal crest, and enormous orbits. Tarsius is 

 one of the very few mammals with a single olfactory foramen on either side of the 

 ethmoid. 



Primates sens, str.).— In Primates the brain overhangs the nasal region so 

 that the cribrosa is horizontal, while the extension of the brain backwards results 



