THE BNTIEE SKULL 475 



through the postorbital process and the tuberosity of the maxillary 

 would form the rest of the outer wall of the orbit and separate it 

 from the zygomatic and temporal fossa3. 



The inner wall of the orbit is triangular, high in front, and meeting 

 the upper and lower walls behind. It is almost flat, but curves out- 

 ward above into the upper wall and below into the lower wall. Its 

 upper two-thirds are contributed by the frontal and the lower third 

 by the lachrymal in front and the palatine and orbitosphenoid behind. 

 The suture between the frontal and these bones is in the main hori- 

 zontal ; it begins at the lachrymal tubercle of the maxillary on the 

 anterior edge, runs backward and downward as the fronto-lachrymal 

 suture, then for an equal distance horizontally as the fronto-palatine 

 suture, then passes backward and upward as the fronto-orbitosphe- 

 noidal suture, and ends by meeting that suture which, as a continuation 

 of the coronal suture, separates the frontal from the alisphenoid, then 

 the alisphenoid from the orbitosphenoid, and terminates below at the 

 posterior part of the orbit in the sphenoidal fissure. From the anterior 

 edge of the sphenoidal fissure a straight suture is continued forward, 

 below the pterygoid line on the orbitosphenoid, and at its anterior end 

 turns sharply upward and meets the junction of the fronto-palatine 

 and fronto-orbitosphenoidal sutures. This is the palato-orbitosphe- 

 noidal suture which separates the orbitosphenoid from the palatine. 

 The only other suture on the inner Avail of the orbit is the straight, 

 nearly vertical lachrymo-palatine suture between the lachrymal and 

 the palatine. At the anterior edge of the orbit are the lachrymal 

 tubercle, the lachrymal groove, and the opening of the lachrymal 

 canal. In some specimens behind the lachrymal bone is an irregular 

 area derived from the ethmoid, known as the os planum. In the 

 palatine behind and below this area, near the lower edge of the wall, 

 are the large spheno-palatine foramen and the small posterior palatine 

 foramen, transmitting blood-vessels and nerves to the nose and the 

 roof of the mouth. At the posterior part of the orbit are two large 

 foramina, whereof the upper, anterior, and smaller is the optic fora- 

 men. It pierces the orbitosphenoid and gives passage to the second 

 cranial or optic nerve and to a meningeal artery ; from the surface 

 round its margin spring the muscles of the eyeball. The larger open- 

 ing behind and below the optic foramen is the sphenoidal fissure. It 

 lies between the orbitosphenoid and the alisphenoid, is irregularly 



