MAMMALIA 



265 



tympanic and the paramastoid process of the exoccipital. The 

 outer face of the periotic bone bears the two foramina, fenestra 

 ovalis and fenestra rotunda, the latter being the posterior. 



The ethmoid completes the cranium in front. The cribri- 

 form plates, perforated for the numerous branches of the 

 olfactory nerve, fill up the space between the sphenoids and the 

 f rentals. They meet in a vertical plate. On the cranial side 

 this forms a slight ridge, the crista galli. On the nasal side it 

 forms the nasal septum and extends forwards, supported above 

 by the frontals and nasals and below by the vomer. The lateral 

 masses are attached to the nasal side of the cribriform plates, 

 and will be referred to 

 with the other tur- 

 binated bones. 



The jugal connects 

 the zygomatic process 

 of the squamosal with 

 the maxilla to form 

 the wide arcade en- 

 closing the temporal 

 and orbital fossae. It 



Nasal 

 Nasoturbinal 



Nasal septum 

 MaxiUoturbinal 



Vomer 



Maxilla 

 Tooth 



FIG. 132. Transverse section of nasal region 

 of skull of sheep. 



also articulates with 

 the small lachrymal 

 which bears the 



opening for the orbital end of the lachrymal duct. The 

 nasals roof the nose, and the side walls and floor of the nose 

 are formed by the premaxillae and the maxillae. The pre- 

 maxillae bear the incisor teeth ; the suture between the 

 premaxilla and the maxilla lies just in front of the prominent 

 canine tooth ; the remaining teeth, the molar teeth, are borne 

 by the maxillae. The palate is formed by the palatine processes 

 of the premaxillae, external to which are the anterior palatine 

 foramina, by the broad palatine processes of the maxillae 

 which meet and fuse in the middle line, and by the palatines. 

 The palatines complete the palate posteriorly, and they also 

 bound the posterior nares. They are associated with the thin 

 vertical pterygoids. 



The vomer is the long median bone which extends from the 

 presphenoid, which it embraces by its bifurcated posterior 



