THE FROG. 39 



of the lateral end of the nasals are the nostrils, while the 

 median ends join the pair of premaxillary bones, which 

 form the tip of the upper jaw. 



At the posterior part of the fronto-parietal a prootic bone 

 extends laterally, forming the roof of the internal ear and 

 meeting laterally a T-shaped squamosal bone; the long 

 arm of the T extending downwards and backwards to- 

 wards the angle of the jaws, a small cartilage (the quadrate) 

 intervening between the squamosal and the lower jaw. 

 The upper jaw is formed of a short splint-like quadrato- 

 jugal, which connects behind with the quadrate and in 

 front with the long, tooth-bearing maxillary bone, and is 

 completed in front by the premaxillaries already referred 

 to. Extending forward and downward from the lower 

 anterior surface of either prootic, and extending a branch 

 backwards to the quadrate, is the pterygoid bone, which 

 joins the maxillary in front, near the lateral end of the 

 nasal bone. Draw a view of the skull from above three 

 times natural size, naming the parts. 



In the ventral view of the skull make out the exoc- 

 cipitals, prootics, sphenethmoid, premaxillaries, maxil- 

 laries, and quadra to jugals as before and see that a large 

 part of the floor of the cranium is composed of an unpaired 

 parasphenoid bone which overlaps the sphenethmoid in 

 front. Beneath and parallel to the nasals are a pair of 

 palatine bones and in front of them and separated from 

 them by a short distance are a pair of teeth-bearing 

 vomers. Draw a ventral view of the skull. 



The lower jaw is composed of a pair of mento-Meckelian 

 bones which meet in front, followed by a short dentary, 

 the posterior end of which is grasped on the inner side by 

 an angular e, which extends back to the angle of the jaw. 

 Notice that on the upper outer side of the angulare a 



