XIII THE SKELETON 233 



gold, a triradiate bone, the inner limb of which attaches 

 to the outer side of the prootic, while the two outer Hmbs 

 diverge, the one running beneath the long stem of the 

 tympanic to connect with the posterior end of the upper 

 jaw, the other extending forward and joining the upper 

 jaw near its middle. The tympanic and pterygoid are 

 separated from each other by a strand of hyaline cartilage. 



(3) The palatines are slender, rodlike bones on the lower 

 side of the cranium, which extend from the anterior end of 

 the ethmoid to the upper jaw. 



The upper jaw, or maxillary arc/i, is composed of three 

 pairs of bones. The posterior portion of the arch is formed 

 by the qnadrato-jugals. These are short bones, devoid of 

 teeth, articulating behind with the pterygoid and tympanic, 

 and joining the maxillary in front by an oblique suture. The 

 maxillaries are the largest bones of the upper jaw ; they 

 connect with the premaxillaries in front, and the quadrato- 

 jugals behind ; they are furnished with teeth throughout 

 their length. On the upper side each bears a frontal pro- 

 cess which is overlapped by the nasal. The intermaxiilaries 

 or pi'ejnaxillaries are the two small bones which form the 

 apex of the maxillary arch ; they are furnished with teeth 

 and are produced backward on the upper side into the 

 facial processes which are instrumental in closing the nares 

 in respiration. 



The lower Jata, or mandibular arch, is composed of a 

 central core, called Meckel's cartilage, which is partly sur- 

 rounded by two membrane bones. The bone at the proxi- 

 mal end is called the angular e, or angulo-spleniaL Meckel's 

 cartilage runs in a groove along the outer side of this bone 

 and widens out at the posterior end, where it forms the 

 facet for articulation with the suspensorium above. A short 

 distance in front of the articulation the angulare bears a 



