94 THE VERTEBRATE SKELETON. 



The lower angle of the quadrate bears a cartilaginous con- 

 dyle with which the mandible articulates. In front of the 

 palatine the cartilaginous snout is overlapped by three mem- 

 brane bones, the jugal, maxilla and preinaxilla. 



The premaxilla (fig. 11, 20), the largest of these, overlaps 

 the maxilla behind ; both bones bear teeth. The jugal (fig. 11, 

 17) lies above the maxilla and overlaps it in front. 



THE LOWER JAW. 



The lower jaw is a strong bar and is like the upper jaw, 

 partly cartilaginous, forming Meckel's cartilage, partly ossi- 

 fied, and sheathed to a considerable extent in membrane bone. 



The outer side and posterior end is ossified, forming the 

 large articular (fig. 11, 21), but the condyle is cartilaginous 

 and the anterior part of the articular forms merely a splint on 

 the outer side of Meckel's cartilage, which extends beyond it 

 for a considerable distance. The angle of the jaw just below 

 the condyle is formed by a small angular (fig. 11, 22), and the 

 anterior two-thirds of the jaw is sheathed in the large tooth- 

 bearing dentary (fig. 11, 23). , 



THE HYOID ARCH. 



The hyoid arch has a number of ossifications in it and is 

 closely connected with the mandibular arch. 



The hyomandibular (fig. 11, 24) is a large bone which 

 articulates with a shallow groove lined by cartilage and formed 

 partly in the pterotic, partly in front of it. The hyomandibular 

 is overlapped in front by the meta-pterygoid, while below it 

 tapers and is succeeded by a small area of unossified cartilage 

 followed by the forwardly-directed symplectic which fits 

 into a groove in the quadrate. 



The unossified tract between the hyomandibular and sym- 

 plectic is continuous in front with a strong bar, which remains 

 partly cartilaginous and is partly converted into cartilage 

 bone. The proximal part is ossified, forming the epi-hyal, the 



