476 MAMMALIAN' ANATOMY 



oval, and transmits the oculomotor, pathetic, and abducens nerves, and 

 the ophthalmic division of the trigeminal nerve, besides blood-vessels 

 supplying the orbit. A slightly arcuate line joining the sphenoiclal 

 fissure and the spheric-palatine foramen marks the upper limit of the 

 area of origin of the external pterygoid muscle. Below this line the 

 inner wall of the orbit passes into the lower wall and faces upward 

 and outward. In or above the suture between the orbitosphenoid 

 and the frontal are two small foramina which lead into the olfactory 

 fossa of the cranium or into the nasal cavity. They are the anterior 

 and posterior ethmoidal foramina, which transmit the ethmoidal 

 vessels and nerves. 



The orbital plate of the maxillary forms the anterior part of the 

 floor of the orbit and passes in front through the infraorbital fora- 

 men. On the inner wall of this foramen, or just behind it, is the 

 anterior dental foramen. The floor of the orbit itself is perforated 

 by many small posterior dental foramina for the nerves and vessels 

 of the upper teeth. At the inner edge of the floor is the straight 

 longitudinal maxillo-lachrymal suture, continued as the maxillo- 

 palatine suture of the orbit backward and slightly outward to the 

 anterior margin of the bony floor. 



THE ZYGOMATIC FOSSAE. 



Each Zygomatic Fossa lies behind the orbit and below the temporal 

 fossa, and, in part, also in front of it. It is triangular, narrow within 

 and wide without ; it communicates above with the temporal fossa and 

 opens below on the lower surface of the skull. The artificial upper 

 limit of the zygomatic fossa is a plane which passes through the upper 

 edge of the zygoma, the anterior edge of the glenoid cavity, and the 

 infraternporal crest on the alisphenoid, and intersects in front the 

 artificial outer plane of the orbit along a horizontal line. The zygo- 

 matic fossa cannot be distinguished from the orbit in front, except 

 artificially by considering as zygomatic all the region behind the 

 imaginary plane described as limiting the orbit externally, and also,, 

 from its direction, posteriorly. The zygomatic fossa is limited in- 

 ternally by the alisphenoid and behind by the front of the basal por- 

 tion of the zygoma. Its outer boundary is the zygomatic arch. On 

 the inner wall of the fossa, just in front of the glenoid cavity, is seen 

 the squamo-sphenoidal suture running upward and slightly backward 



