THE SKULL. 2$ 



them to cover in a region which, in. most cases, is pro- 

 tected by the alisphenoid. This bone is small and closely- 

 attached to the middle third of the ventral margin of 

 the parietal in the skull of the Slider. 



47. The palate bones lie in front of the pterygoids. 

 They partly bound the posterior nares above, and also 

 form a small part of the roof of the mouth on the sides 

 of the recess in which the posterior nares open. Above 

 they meet the pterygoids, and externally the superior 

 maxilla. Between them lies — 



48. The vomer, a slender bone having on its anterior 

 extremity a knob which ■ appears on the roof of the 

 mouth. With the palate bones it completes the roof 

 of the posterior nares. * 



49. Meeting in the middle line at the front of the 

 skull are the small premaxilla, which bear part of the 

 horny cutting-ridges of the upper jaw. 



50. The maxilla lie on the outer sides of the pre- 

 maxillae, and form the greater part of the roof of the 

 mouth and of the upper boundary of the gape ; they 

 also form a large part of the floors of the orbits. 



51. The naso-prefrontal bones roof in the front part of 

 the nose chamber. In front they join the maxillae, and 

 help to complete the orbital boundary. Behind they 

 join — 



52. The frontal bones, which meet in the middle line 

 above the orbits. Behind, these articulate with the 

 parietal and post-frontal bones, and in front with the 

 naso-prefrontal bones. 



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