THE SKULL. 57 



iii. The quadratojugal is a short bone forming the pos- 

 terior part of the margin of the upper jaw. 



iv. The maxilla is a long thin bone forming the greater 

 part of the margin of the upper jaw : it bears 

 teeth along its whole length which are anchylosed 

 with the bone. It is connected behind with the 

 quadra tojugal ; about the middle of its length 

 with the anterior limb of the pterygoid and with 

 the palatine ; and in front with the premaxilla. 



V. The premaxilla is a small bone which meets its 

 fellow in the middle line in front, and so com- 

 pletes the margin of the upper jaw : like the 

 maxilla it bears teeth. It gives off on its dorsal 

 surface a backwardly projecting process which 

 forms part of the inner boundary of the nostril. 



1). The Mandibular Arch, The upper part of the arch 

 remains unossified as the quadrate cartilage, which 

 forms the suspensorium, i.e., serves to connect the lower 

 jaw with the skull : this is a rod of cartilage which is 

 fused above with the auditory capsule, and runs down- 

 wards and backwards to the angle of the mouth, where 

 it is connected with the hinder end of the quadratojugal 

 bone. In the adult frog, the quadrate cartilage lies 

 between the squamosal and pterygoid bones, and is 

 almost completely concealed by these. The lower part of 

 the arch persists in part unossified as Meckel's cartilage, 

 which forms the basis of the lower jaw, and is ensheathed 

 by cartilage-bones and membrane-bones. 



i. The squamosal is a T shaped bone, the stem of 

 which is closely applied to the outer surface of the 

 quadrate cartilage. The posterior limb of the T 

 is attached to the outer surface of the auditory 

 capsule, and with the body of the squamosal 

 helps to support the annulus tympanicus. 



ii. The angulosplenial ensheaths the inner and lower 

 surfaces of Meckel's cartilage along the greater 

 part of its length : near its hinder end it is 

 produced upwards into the coronary process. 



