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ESSENTIALS OF ZOOLOGY 



and pterygoids, the inner arcade. The palatine lies trans- 

 versely between the sphenethmoid and the maxilla and supports 

 the nasals above. It gives articulation to the pterygoid, a 

 long graceful bone resolved into three processes : an anterior, 

 articulating with the palatine and abutting against the maxilla ; 

 an inner, articulated to the prootic ; and a posterior, which 

 extends to the posterior end of the upper jaw and supports the 

 squamosal. The squamosal is a prominent T-shaped bone. 

 The upper inner limb of the bone is articulated to the prootic, 



Premaxitta 



Vomer 

 Palatine 



Maxilla 

 Pterygoid 



Parasphenoid 



Fenestra walls 

 Quadrato-j 



Nasal capsule 



Palato-pterygoid 

 Sphenethmoid 



Prootic 



Exoccipital 

 Quadrate 



FIG. 102. Ventral view of frog's skull. See explanation of fig. 101. 



and the lower extends to the end of the upper jaw, where it 

 covers the quadrate cartilage. 



The lower jaw is developed around the mandibular or 

 Meckel's cartilage and consists of an anterior dentary, which is, 

 however, toothless, and a posterior angulo-splenial. 



The columella auris is, from its method of appearance and 

 its position, looked upon as a product of the upper part of 

 the hyoid arch. The rest of the hyoid arch persists. Just 

 below the fenestra ovalis the anterior cornu of the hyoid, 

 the elongated hyoid arch, fuses with the auditory capsule, 

 and the arch forms a graceful curve to reach the anterior face 

 of the flat body of the hyoid bone. This bone is produced by 

 the fusion of the basal elements of the larval hyoid and the 



