462 MAMMALIAN ANATOMY 



greater than its greatest width. The surface is convex in both direc- 

 tions, but varies in degree at different points. It presents (1) a median 

 portion which is wide behind and narrow in front ; (2) narrow, lateral 

 zygomatic arches which unite laterally the anterior portion, or face, 

 to the posterior portion, or cranium, and bound externally large, irreg- 

 ular openings. In front of the middle of this central portion, on each 

 side, is a pointed projection, the frontal postorbital process, which by 

 joining the postorbital process of the malar converts the large lateral 

 opening bounded externally by the zygoma into an anterior orbital 

 fossa and a posterior temporo-zygomatic fossa. The face occupies 

 the anterior fourth of this view, and has been already studied from in 

 front; the present aspect shows clearly its sloping disposition, inasmuch 

 as its entire surface, with the exception of the small external portion 

 under the orbital rim, is visible. 



The superior surface of the cranium is pointed in front, receiving 

 the upper ends of the nasal bones between the frontal nasal processes, 

 on the outer sides whereof lie the upper ends of the maxillaries. The 

 posterior outline is the sharp lambdoidal crest, which is transverse in 

 the middle but slopes forward and downward on each side. At its 

 centre is the external occipital protuberance, more or less prominent, 

 continued forward on the interparietal bone as the sagittal crest. The 

 superior surface of the cranium is flat between the postorbital pro- 

 cesses or only slightly convex from before backward and from side 

 to side. In the present position it faces slightly forward as well as 

 upward. Behind the postorbital processes the superior surface is 

 convex from before backward and becomes more and more convex 

 transversely, facing upward, outward, and backward, until the maxi- 

 mum is reached at the transverse line joining the auricular points 

 which are the centres of the external auditory meatuses. Behind this 

 line the superior surface becomes less convex transversely, sloping 

 downward, outward, and forward. The region lying on each side and 

 in front of the lambdoidal crest is concave from before backward. 

 Except at the orbital rims, the superior surface passes downward with- 

 out a distinct line of demarcation into the lateral surfaces. Curving 

 inward and backward from the upper surface of the postorbital pro- 

 cesses are the slightly sinuous temporal ridges, which in well-marked 

 skulls terminate by meeting at the middle line near the posterior end 

 of the parietals. They mark the superior boundary of the area of 



