the anterior wall ; [2], the maxillae forming the lateral 

 portion of the floor and lower part of the side wall; [3], the 

 prefrontals contributing the upper part of the side wall, 

 the whole of the roof, and major portion of the posterior 

 wall, and [4], the vomer forming the remainder of the 

 posterior wall. Two recesses of the cavity are recognis- 

 able, a superior and an inferior, the former (reccssus 

 superior) is that portion of the cavity surrounded on three 

 sides by the prefrontal bone, the latter (reccssus inferior) 

 is situated well to the front of the cavity in the region of 

 the maxillo-premaxillary suture, just behind the nasal 

 laminae of the premaxillae. The superior recess lodges 

 two nasal sinuses, one of which is the true, physiological, 

 olfactory sac, the inferior recess, one sinus. The nasal 

 fossa extends back above the lower sinus and below the 

 upper two sinuses. The posterior wall of the cavity is 

 very imperfect (Figs. 44 and 46). In the mid line is the 

 V-shaped ethmoidal Assure [38] which intervenes between 

 the nasal plates of the prefrontal hours on either side, the 

 ethnoidal sulcus of the vomer below, and the transverse 

 fronto-pref rontal suture above. This fissure is incompletely 

 closed by the cartilaginous capsule and septum nasi, and 

 through the upper part on either side of the septum the 

 olfactory nerves enter. On either side, below the ethmoid 



prefrontal [59], medially the ante 

 prefrontal processes [00] of the vo 

 premaxillary suture, laterally p 

 maxilla [1] immediately within tin 

 in the roof thereof is the lachrymal 

 able size, in the absence of cai 

 bounded in front by the nasal hi 

 behind by the orbital plate of the 



