518 MAMMALIAN ANATOMY 



On the inner wall, at the upper anterior part, between the ptery- 

 goid plate and the maxillary, is the vertical ptery go -maxillary fissure 

 leading into the spheno-maxillary fossa. From the top of this fissure 

 the spheno-maxillary or inferior orbital fissure passes forward and 

 outward between the spheno-maxillary crest on the sphenoid and the 

 tuberosity of the maxillary ; it represents the wide aperture of com- 

 munication seen in the cat between the zygomatic fossa and the orbit. 

 On the roof of the zygomatic fossa is the oblique squamo-sphenoidal 

 suture, and on the outer wall the malo-temporal or zygomatic suture. 



The spheno-maxillary fossa cannot be clearly seen from the ex- 

 terior. Its inner wall is formed by the vertical plate of the palatine 

 and is pierced by the spheno-palatine foramen. The ptery goid pro- 

 cess limits it behind, and exhibits the foramen rotundum and the 

 anterior openings of the Vidian and pharyngeal, or ptery go -palatine, 

 canals. Its roof is the under surface of the great wing of the sphe- 

 noid. A small portion of the zygomatic surface of the maxillary and 

 the orbital (ethmoidal) process of the palatine limit it in front. It is 

 wide above and narrow below, where it ends in the posterior palatine 

 canal. (See page 332.) 



On the lateral aspect of the skull, behind the zygoma, is the small 

 auditory meatus, bounded below by the tympanic plate, above by the 

 ridge known as the posterior root of the zygoma, and behind by the 

 great mastoid process. 



Above the temporal line in front is the frontal eminence, and near 

 the line behind is the parietal eminence. 



The exterior of the skull often presents, on the line of the sutures, 

 small irregular bones which are not sufficiently constant to receive 

 special names ; they are known generally as sutural or Wormian bones, 

 or ossa triquetra. They are found most frequently in the lambdoidal 

 suture. A single bone occurring very often at the pterion is known as 

 the epipteric bone. 



THE CRANIAL CAVITY. 



The interior of the human cranium is exposed by a transverse 

 horizontal section through the ophryon and the occipital point. It is 

 characterized by its globular form and by shortness of base, measured 

 from the occipital foramen to the cribriform plate of the ethmoid. It 

 differs from the cranial cavity of the cat in not possessing a bony 

 tentorium, but especially in the greater size of the anterior and poste- 



