62 THE AMERICAN BEAVER. 



is also attached to the under surface of each nasal a 

 long curved bone overlapping the turbinate, and serv- 

 ing to retain it in its position. 



In addition to the ridges or crests which have been 

 described, there are the parietal crests; these start 

 from the interparietal crest, and, diverging, terminate 

 at the junction of the temporals and frontal. Their 

 usual form is represented in the top view of the skull, 

 but it is subject to much variation. There is a straight 

 glenoid crest at the junction of the temporal and 

 sphenoid. The top of the hook process of the jugular 

 bone forms a crest continuous with the sharp upper 

 edge of the malar. Delicate ridges extend from the 

 outer margins of the incisive foramina to the front 

 edge of the alveolar processes, and from the temporal 

 jugular process a crest extends backward toward the 

 posterior point of the parietal. 



The incisive foramina are in the intermaxillaries 

 midway between the incisors and the molars. The 

 spheno-palatine foramen^ is just behind the orbital 

 opening of the ante-orbital foramen, and opens into 

 the nostril at the junction of the ethmoid and the 

 s. maxillary. The small optic foramen is in the ala 

 of the pre-sphenoid above the transverse opening in 

 the body of the bone. The pterygo-palatine' is lower 

 than the optic, and opens in the anterior part of the 

 palatal bone. The external pterygoid plate is pierced 

 with a large foramen which communicates with the 

 sphenoidal fissure by what Cuvier calls the Vidian 

 canal. The condyloid foramina are in front of the 



^ These foramina are named from analogy, the first is entirely 

 in the maxillary, and the second in the maxillary and the palatal. 



