THE SKELETON. 51 



branch of the fifth nerve. This foramen is between the 

 alisphenoid and the orbitosphenoid. The other two 

 foramina, rotundum and ovale, transmit the second and 

 third divisions of the fifth nerve. 



The pterygoid portion of the sphenoid is a paired bone 

 (Figs. 17 and 18) lying on either side of the cephalic 

 half of the basisphenoid and the caudal half of the 

 presphenoid. In the adult cat the sutures are some- 

 times obliterated so that this bone appears as a caudal 

 continuation of the palatine. The two pterygoid bones 

 or plates form the descending walls, and, together with 

 the median portion of the sphenoid, the roof of the 

 mesopterygoid fossa, whose cephalic continuation is the 

 posterior nares. From the ventral posterior angle of 

 each projects the hamular process, dorsal of which is 

 seen the small external pterygoid process. Between the 

 bases of the hamular and the external pterygoid processes 

 is the small external pterygoid fossa. 



The presphenoid bone is the narrow median bone ex- 

 tending from the basisphenoid to the vomer. It contains 

 within it two large sinuses into which project the ventral 

 scrolls of the ethmoturbinal bones. The alisphenoids 

 enter into the formation of the mesal walls of the orbits 

 and are perforated at their bases by the optic foramina, 

 through which pass the optic nerves. 



BONES OF THE FACE. 



There are seven paired bones in the face and two 

 single ones, making in all sixteen. 



The premaxillary, with its fellow, extends ventrad and 

 laterad of the anterior nares. These bones bear the six 

 incisor teeth. The anterior palatine or incisor foramina 

 connect the oral cavity with that of the anterior nares. 



