348 



CHORD ATA. 



and lies between the two orbits. Its front end is surrounded 

 by a girdle bone, the sphenethmoid. Its walls are formed of 

 cartilage, in the roof of which are a large anterior fontanelle 



Fig. 245.— Ventral View of Frog's Skull. 



Cartilage black, Bones white. 

 Premaxilla. 



Vomer. 



Maxilla. 

 Sphenethmoid, 



Parasphenoid. 

 Pterygoid. 



Quadrate. 



Internal Nas. 

 Palatine. 



Quadratojugal. 



Prootic. Exoccipital. Columella. 



and a small pair oi posterior fontanelles^ as in the skate. 

 The fontanelles are not seen, as they are covered up by a 

 pair of large membrane-bones, \k\Q frontoparietals. Ikying 



Fig. 246. — Dorsal View of Frog's Skull. 



Cartilage black, Bones white. 

 Premaxilla. 



External Nas. 



Exoccipital. 



Prootic. 



Sphenethmoid. 

 Frontoparietal. 



Quadratojugal. 



Quadrate. 



under the cranium is a long dagger-shaped bone, \\\^ para- 

 sphenoid. At the hind-end of the cranium is a pair of bones, 

 the exoccipitals, each of which bears an occipital condyle. 

 Anteriorly the cranial cartilage is continuous with the 



