38 



MAMMALIAN DENTITION 



tions of tooth structure one or two of which may be mentioned 

 as of special significance for our purpose. 



The jaws of the Iguana (Fig. 6) show an experiment of 

 Nature in producing a type of tooth somewhat more complicated 

 than the simple cone. Careful examination of these shows that 

 most have not one single point or tip but several, often seven 

 in fact, of which the central one is the largest and the most 

 prominent. We see then that by very little modification a 



Fig. 6. — Jaws of Iguana (Iguana tuberculata, 81.1-1). This is an experiment of 

 Nature in producing teeth with more than one tip or cone. The simpler teeth are 

 these in. the front of the mouth; the more advanced occur further back near the areas 

 of muscular attachment. 



tooth with many tips can originate. A further point which is 

 worth our careful attention is that in the Iguana the teeth near 

 the front of the mouth and below the nostril retain almost 

 without exception the simple conical form. The more com- 

 plicated teeth in this animal are most numerous further back 

 on the jaws near the areas of muscular attachment. 



The skull of the Mississippi Alligator (Fig. 7) shows that 

 certain teeth may consistently grow to a greater size than 



