THE BOXES OF THE SKULL 195 



backward from the palatine bridge. Its medial surface is divided 

 by a low ridge into a dorsal portion, in particular relation to the 

 nasopharynx, and a ventral portion, in relation to the oral cavity, 

 the ridge indicating the position of the soft palate. Its lateral 

 surface is partly applied to the maxilla and partly exposed to the 

 orbit. Its dorsal margin is articulated with the presphenoid and 

 with the ethmoidal process of the orbitosphenoid, but a small 

 posterior portion is free, so that the anterior portion of the basi- 

 sphenoid is visible from the orbit. The free ventral margin forms 

 posteriorly a thick projecting angle, the pyramidal process (pro- 

 cessus pyramidalis), the base of which is cleft where it articulates 

 with the medial and lateral laminae of the pterygoid process. 

 Between the pyramidal process and the alveolus of the last cheek- 

 tooth there is a conspicuous palatine notch (incisura palatina), 

 connecting the orbit with the palatal surface. In the entire skull 

 only the posterior portion of the lateral surface is visible from the 

 orbit, the anterior portion being concealed by the projecting bases 

 of the posterior cheek-teeth. The ridge of bone on which the 

 alveoli of these teeth are borne is separated from the palatine bone 

 by the infraorbital groove. The medial wall of the latter, formed 

 by the palatine bone, contains the orbital opening of the pterygo- 

 palatine canal and the sphenopalatine foramen. 



The Mandible 

 The mandible (mandibula) or lower jaw comprises the tw^o 

 dentary bones (ossa dentalia), which, in the rabbit, as in mammals 

 generally, are united by a fibrous or fibrocartilaginous connection 

 (symphysis mandibulae); not coalesced, as in the human skull, to 

 form a continuous structure. As indicated above, each of the 

 dentary bones comprises: (1) a horizontal, tooth-bearing portion 

 which, in conjunction with that of the opposite side, forms the 

 body of the mandible (corpus mandibulae); and (2) a posterior, 

 vertical plate, the mandibular ramus (ramus mandibulae), for 

 muscle attachment and articulation. The horizontal portion is 

 deep posteriorly, where it lodges the alveoli of the cheek-teeth. 

 Anteriorly, in the diastema separating the latter from the incisors, 

 its dorsal surface is rounded and depressed, the space thus formed 

 corresponding to a similar space in the upper jaw and serving 



