THE ENTIEE SKULL 521 



tympanum, the tegmen tympani, lies lateral to this eminence. The 

 superior border of the petrous is grooved by the superior petrosal sinus, 

 and the posterior border near the basioccipital by the inferior petrosal 

 sinus. On the posterior surface of the petrous are the internal 

 auditory meatus, the variable floccular fossa, and the opening of the 

 aquaeductus vestibuli. 



On each side of the foramen magnum, in front, is the posterior 

 opening of the anterior condyloid canal for the twelfth cranial nerve, 

 and between the occipital and the petrous is the irregular posterior 

 lacerated or jugular foramen, which transmits the ninth, tenth, and 

 eleventh cranial nerves, the internal jugular vein, and the meningeal 

 branch of the ascending pharyngeal artery. From the jugular fora- 

 men, the wide groove for the lateral sinus curves upward and backward 

 on the temporal, the parietal, and the occipital bone ; it meets the 

 groove for the other lateral sinus and the vertical groove for the 

 superior longitudinal sinus near the internal occipital protuberance. 

 The internal occipital crest passes upward from the foramen magnum 

 to the protuberance. 



