46 THE SKELETON OF THE FROG 



group of pointed teeth, and forms the inner 

 boundary of the posterior narial opening of its 

 side. 



3. The Jaws consist of two cartilaginous arches on each side, 

 maxillary and mandibular, in connection with which 

 cartilage-bones and membrctne-hones are developed. 

 Each arch meets its fellow in the middle line in front ; 

 and the maxillary arches, forming the upper jaw, are 

 firmly connected with the cranium by anterior and 

 posterior bony struts. 



a. The Maxillary Arch. 



Q H 



Fig. 9. — The frog's skull from the right side. 

 A, parasphenoid ; AS, angulosplenial ; B, anterior cornu of hyoid ; 

 C, columella ; D, dentary ; E, exoccipital ; F, nostril ; FP,^ fronto- 

 parietal; H, body of hyoid; L, aperture for exit of optic nerve; 

 M, maxilla ; MM, mentomeckelian ; M', aperture for exit of fifth and 

 seventh nerves^ "H, nasal; O, pro-otic ; p, pterygoid ; PM, premaxilla; 

 Q, " quadratojugal " ; R, aperture for exit of ninth and tenth nerves ; 

 S, squamosal ; SE, sphenethmoid ; T, posterior cornu of hyoid. 



i. The pterygoid* is a large triradiate bone, the inner 

 limb of which is connected with the auditory 

 capsule ; while the posterior limb runs back to 

 the angle of the mouth, and the anterior limb 

 forwards along the upper jaw to the palatine 

 bone. 



ii. The palatine* is a slender transverse bone, con- 



• These, originally cartilage-bones, become more or less ensheathed 

 by membrane-elements in the course of development. 



