58 



GENERAL ZOOLOGY 



goid can be seen in a ventral view of the skull (Fig. 32). Begin- 

 ning at the angle of the jaw, it curves forward beneath the stem 

 of the squamosal to the upper jaw at its middle where it is also 

 connected to the lower end of the cross piece of the squamosal by 

 cartilage. From the center of this arched portion of the ptery- 

 goid bone an arm projects medially to the outer end of the prootic 

 bone. Each palatine bone extends from the anterior end of the 



exoccipifal 

 pterygoid- 



squamosal 



fronhpariefo/^ 



sphenethmoid 

 ■nasal 



parte faL 

 iemporal/ 



angulare 



-pre- 



maxil/ary 



=^~- S> menfo- 

 dentale Meckelian 



frontal 



■superior 

 maxillary 



Fig. 



occipital 

 mastoid process 

 inferior maxillary 



33. — Side view of skull Rana catesbeiana and of human skull, reduced in 

 size for purpose of comparison. 



sphenethmoid outward to the upper jaw, directly beneath the 

 lateral processes of the nasal bones. 



Jaws of the Frog. — The upper jaw is composed of three pairs of 

 bones. In front are the two premaxillary bones, short segments, 

 from each of which a short facial process curves upward and back 

 toward the external nares. A maxillary bone forms the long 

 segment, on either side, extending from the premaxillary in front 

 to the quadratojugal bone behind. The quadratojugal bone 

 articulates with the squamosal and pterygoid bones at its 

 posterior end. Teeth are borne by the premaxillary and maxil- 

 lary bones (Fig. 33). 



