THE SKULL THE CEANIUM 259 



the basioccipital. Its outer angle, known as the petrosal process, 

 is separated on each side from the remaining part of the border by a 

 deep, narrow notch, directed inward as well as forward. The petrous 

 of the temporal is applied to the under surface around the notch, and 

 a little pointed process from the entotympanic fills the notch which is 

 part of the middle lacerated foramen of the skull. 



The rest of the flattened part of the upper surface of the basi- 

 sphenoid consists of a narrow strip on each side of the sella turcica, 

 the long axis of which is directed obliquely inward and forward. It 

 is limited within, beginning in front, by the inner edge of the ptery- 

 goid process, the outer side of the olivary eminence, the side of the 

 sella, and the outer side of the clivus. Its external margin is in 

 front the outer edge of the pterygoid process and for the rest of the 

 distance a sharp crescentic border, which is at once the overhanging 

 upper margin of the foramen rotundum and foramen ovalis and the 

 inner edge of the alisphenoidal part of the tentorium. The jagged 

 margin of the pterygoid process limits the region in front. Behind, 

 overlapped extracranially by the petrous, is the oblique external margin 

 of the notch already mentioned. Just lateral to its outer angle and 

 medial to the beginning of the posterior margin of the tentorial part 

 is a smaller notch, which, with the petrous, forms a foramen leading 

 into the tympanic cavity in the temporal bone. It represents the 

 outer part of the middle lacerated foramen, and transmits the Vidian 

 and small superficial petrosal nerves. The little point between the two 

 notches is known as the lingula of the sphenoid. 



The region anterior to the olivary eminence may be considered the 

 superior surface of the pterygoid process. It is almost square ; the 

 anterior border is jagged, and bevelled at the expense of the anterior 

 third of the surface. Its inner third is flat and rough, and articulates 

 with the presphenoid (Figs. 187, 188). An oblique line runs back- 

 ward and outward from the middle of the outer edge of this rough 

 area to join the sharp anterior external edge of the plate which forms 

 the floor of the sphenoiclal fissure and the roof of the round foramen. 

 In front of this line is an external anterior triangle which is concave 

 from side to side and inclines upward and outward. The outer border 

 of this surface is directed slightly outward, and is produced at its 

 middle into a spine, called the external pterygoid process. The 

 surface is seen at the lower posterior part of the orbit, where it is 



