/D COMPAKATIVE DENTAL ANATOMY 



rows. One of the upper rows is situated on the 

 maxillae and the other on the palates. In the alii- 



Fig. 24. — Myliobatis, showing occlusion of tooth-bearing surfaces. 



gators and crocodiles there is one row above and 

 one below, but no occlusion of the individual teeth. 



Fig. 25. — Skull of Alligator (Alligator mississippiensis), showing oc- 

 clusion of rows of teeth. 



The teeth of some of the primitive birds were also 

 arranged this way (Fig. 25). 



We next find occlusion of individual teeth, on 

 which there has been no development of extra 



