THE SKULL 47 



necting the upper jaw with the anterior end of 

 the sphenethmoid. 



iii. A short bone forming the posterior part of the 

 outer margin of the upper jaw, is in the position 

 of the quadratojugal of other skulls. 

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

 part of the outer margin of the upper jaw : it bears 

 teeth along its whole length which are anchylosed 

 with the bone. It is connected behind with the 

 " quadratojugal " ; 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 outer 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, 

 vi. The quadrate cartilage, which forms the suspen- 

 sorium, i.e., serves to connect the lower jaw with 

 the skull, 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. 



vii. 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. 



b. The Mandibular Arch. The arch persists in part un- 



ossilied as Meckel's cartilage, which forms the basis of 



the lower jaw, and is ensheathed by cartilage-bones and 



membrane-bones. 



i. The angulosplenial ensheathes the inner and lower 

 surfaces of Meckel's cartilage along the greater 



