SECTIONS, 53 
A thin vertical plate of bone, articulating ante- 
riorly with the palatine, and lying beneath 
the pre-sphenoid and orbito-sphenoid, is the 
pterygoid. 
B. Transverse Section through the posterior 
portion of the Skull. (Fig. 8). 
In the left hand of the section the periotic is shown 
lying dorsal to the tympanic bulla. Notice on 
the right hand side, that a portion of the 
anterior wall of the tympanic bulla has been 
cut through, and laterally the external auditory 
meatus. Dorsally, the prominent sagittal crest 
forms a median prominence. The parietals 
form the dorso-lateral boundary of the section, 
the ventral and lateral portions being com- 
pleted by the squamosals. Lying on the inner 
border of the squamosal, notice the periotic. 
In the section of the bulla, notice that the cavity 
is imperfectly divided into two chambers by 
an incomplete bony septum, arising from the 
anterior wall. The inner chamber terminates 
blindly ; while into the outer, the Eustachian 
tube enters. The somewhat prominent lip of 
the external auditory meatus, is well seen in 
section. .Om.the inmer sidevof the? section: 
notice the cut portion of the carotid canal. 
C. Transverse Section passing in front of the 
fronto-parietal suture, and the anterior 
border of the pre-sphenoid. (Fig. 9). 
The dorsal portion of the section. is formed by the 
