140 THE SKULL [CHAP. 



The naso-palatine nerve descends through them to spread 

 over the anterior surface of the soft palate. Not far from 

 the hinder border of the palate, and more distant from the 

 middle line, near the suture between the maxilla and palatine, 

 are several much smaller foramina (posterior palatine), also 

 for the transmission of branches of the fifth nerve and blood 

 vessels. 



The truncated median part of the hinder edge of the 

 palate forms the lower margin of the posterior narial aperture. 

 Laterally, the palate bones are continued backwards as 

 vertical plates, thick and rounded below at first, but gradually 

 becoming more compressed. These are continued still 

 further backwards by the compressed pterygoid bones (Pt), 

 ending in the backward projecting hamular processes, and 

 supported externally by the descending (pterygoid) plate of 

 the alisphenoid. The groove between these descending 

 lamellae of bone continues the narial passage backwards. It 

 has for its roof the vomer ( Vo] in front, then the presphenoid 

 (PS), and posteriorly a portion of the basisphenoid (BS) ', 

 but the palatines and pterygoids arch over so much towards 

 the middle line that they only leave a small strip of these 

 bones exposed. Inferiorly, this groove is not closed by 

 bone, but in the living animal the soft palate is stretched 

 across it. 



The base of the skull, behind this " mesopterygoid " fossa 

 presents in the middle a nearly flat elongated surface, con- 

 sisting of the basisphenoid (-BS) and basioccipital (-BO] ; the 

 latter, roughened for the attachment of muscles and ter- 

 minating posteriorly at the inferior border of the foramen 

 magnum (////), flanked on each side by the occipital 

 condyles (oc). The nearly straight lateral edges of the 

 anterior half of the basioccipital rise up to abut against the 

 prominent smooth rounded auditory bullce (Tj), which form 



