466 MAMMALIAN ANATOMY 



are the anterior edges of the orbital openings. They are straight near 

 the lateral borders, and deeply rounded and emarginate within. The 

 median third forms the lower edge of the posterior nares. In the 

 middle line it is slightly prolonged backward as the postnasal spine, 

 which gives attachment to the azygos uvulae muscle. On each side 

 of this middle third the posterior border of the hard palate is con- 

 tinued backward as the edges of the middle pterygoid fossa. The 

 hard palate is formed of the palatine plates of six bones, the two 

 premaxillaries in front, the two maxillaries in the middle, and the 

 two palatines behind. It is divided into two halves by the median 

 mesopalatine suture. The premaxillo-maxillary sutures run from 

 the lateral border inward and slightly backward and come together 

 in the middle line at the junction of the anterior and middle thirds. 

 The transverse palatine suture is seen a little behind the middle. It 

 runs transversely for a short distance only, and then bends sharply 

 backward and outward, reaching the posterior border on each side not 

 far from its external end. It separates the maxillaries from the pala- 

 tines. Behind the incisors are several small vascular, incisive foramina, 

 and on each side of the middle line in front are the large, oval anterior 

 palatine foramina transmitting the nasal arteries and the nasopalatine 

 nerves. Further back, behind the middle, at some distance from the 

 mesopalatine suture, are the anterior openings of the posterior palatine 

 canals for the palatine vessels and nerves. 



The hard palate is, in the main, flat, but on each side is a curved, 

 longitudinal ridge, which begins at the posterior end of the anterior 

 palatine foramen, extends backward and slightly outward, and ends, 

 sometimes in a distinct swelling, behind the posterior palatine foramina. 

 In some specimens external to this ridge is a faint groove for the 

 palatine vessels. The thick, tough mucous membrane of the mouth is 

 firmly attached to the entire surface of the hard palate. 



The middle pterygoid fossa lies between the orbito-zygomatic open- 

 ings behind the palate and in front of the expanded cranial portion. 

 It occupies the middle fifth of the length and the entire width of the 

 under surface of the skull. Its own length is one-third greater than 

 its width. It is only half as high as wide. From in front it slopes 

 slightly downward and backward ; from side to side it is strongly 

 concave. Its anterior wall is limited to the narrow posterior edge of 

 the palatine plate of the palatine, which forms the floor of the pos- 



