512 MAMMALIAN ANATOMY 



lateral to which is the malo-maxillary suture joining the prominent 

 malar to the depressed maxillary. The pyriform nasal aperture is 

 divided vertically by the anterior edge of the nasal septum, formed 

 by the mesethmoid above and the vomer below. At the side of each 

 nasal cavity may be seen the maxillo-turbinal, separating the inferior 

 and middle meatuses ; further back and higher up is the middle tur- 

 binated bone. 



UPPER ASPECT. 



When the human skull is viewed from above its outline is oval, 

 because it is the outline of the vault of the cranium ; the only parts of 

 the face which are visible are the ends of the nasal bones and in some 

 specimens the edges of the zygomatic arches. The superior aspect of 

 the cat's skull exhibits the face as well as the cranial vault. The out- 

 line in man is formed of the frontal, the parietals, and the upper, or 

 interparietal, portion of the occipital bone. The frontal is joined to 

 the parietals by the transverse coronal suture ; the sagittal suture 

 runs backward from the bregma, at the middle point of the coronal 

 suture, to the lambda, at the middle of the transverse occipito-parietal 

 or lambdoidal suture. In some skulls the sagittal suture is retained 

 between the two frontal bones ; this portion is termed the metopic 

 suture ; it usually persists in the adult as a fissure in the frontal 

 bone just below the glabella. The parietal bones exhibit the parietal 

 eminences, and, near the sagittal suture behind, the parietal foramina, 

 marking the obelion, the point at which the sagittal suture begins to 

 disappear with advancing age. 



POSTERIOR ASPECT. 



The posterior aspect of the human skull presents, at the lower part, 

 that portion of the occipital bone situated above the external occipital 

 protuberance, and, at the upper part, the two parietals ; at the sides 

 are the squamosals. 



Its outline is almost circular, but flattened somewhat at the inferior 

 margin along the superior curved line. Below, far in advance, is seen 

 the posterior aspect of the lower jaw. Near each lower outer corner 

 is the asterion, a point where the lambdoidal, occipito-mastoid, and 

 parieto-mastoid sutures meet. On the greatest posterior projection 

 of the occipital bone is the occipital point. The external occipital 

 protuberance marks the inion. 



