34 



MANUAL OF ELEMENTARY ZOOLOGY 



-p.m. 



membrane bone known as the palatine. 1 At its outer end 

 the cartilaginous bar turns backwards, and here another 

 membrane bone, the pterygoid, 1 fits against its inner 

 side. The pterygoid is Y-shaped, with the fork directed 

 backwards, the inner branch of the Y abutting on the 

 auditory capsule. The outer branch underlies the main 

 branch of the squamosal, and between these two bony rods 

 there projects outwards from the auditory capsule a rod of 

 cartilage, the quadrate, continuous with the longitudinal 

 bar. With the quadrate, held firm as it is by processes 



of the squa- 

 pro. /.p. pt. m o s a 1 a n d 



**' *■ pterygoid, ar- 



ticulates the 

 lower jaw, for 

 which the 

 structures in 

 question are 

 said to form the 

 suspensorium. 

 The outer series 

 of bones of the 

 upper jaw 

 begins with the 

 premaxilla, a 

 small mem- 

 brane bone 

 applied to the 

 front of the 

 nasal capsule, 

 on to whose upper surface it sends a process. The two 

 premaxillse meet in the middle line, forming the tip of the 

 upper jaw, and each of them bears a row of teeth. Behind 

 the premaxilla, on each side, another membrane bone, the 

 maxilla, continues the edge of the jaw. The maxilla is a 

 long slender bone which bears a row of teeth. Along 

 the greater part of its length it is supported by the nasal 

 capsule and pterygoid, but the hinder part lies free till it 



1 The palatine and pterygoid are cartilage bones in most of the 

 animals in which they occur. In the frog the cartilage bone is 

 replaced in development by membrane bone. 



a.sp. 



Fig. 15.- 



-The skull of a frog, seen from the 

 right side. 



., Anterior cornu of hyoid ; a.sp., angulo-splenial ; b., 

 body of hyoid; col., columella; d., dentary ; e.n., 

 external narial opening;,/!/., fronto-parietal ; m., 

 maxilla; mm., mentomeckelian ; «., nasal ; o.c, occi- 

 pital condyle ; p.c, posterior cornu of hyoid ; p.m., 

 premaxilla; pro., prootic ; ft., pterygoid; q., quad- 

 rate; q.j., quadratojugal ; sp., sphenethmoid ; sq., 

 squamosal. 



