238 PETRIFACTIONS AND THEIR TEACHINGS. CHAP. III. 



smooth, and the fang entirely absorbed in consequence of the 

 pressure of a successional tooth. 



In other specimens in the Museum, the crown is reduced 

 to a mere plate of coarse dentine, flat above, and slightly 

 concave beneath ; a proof that the teeth remained attached to 

 the alveolar process, till the fang was entirely absorbed, and 

 the new crown ready to pierce the 

 gum, and take part in the process 

 of mastication. The removal of the 

 fang by absorption is manifest in 

 almost every specimen, as I pointed 

 out in my earliest memoir on the 

 subject ; l and the effect of this pro- 

 cess may be traced through every 

 gradation, in like manner as the 

 destruction of the crown of which 

 I have already spoken. Now it is 

 the power of perfect mastication 

 possessed by the colossal reptile to 

 which these teeth belonged, and of 

 which we have such unquestionable 

 proofs in the specimens before us, 

 LTGN. 52. that is so marvellous a fact to the 



UPPER TOOTH OF THE IGUANO- 7nn i o ~;<,t W V, O rp flpr>t tW flip PWPTI 

 DON: WITH THE CROWN WORN ZOOlOglbl, WI1C 



FLAT, AND THE FANG ABSORBED, tial conformation of the jaws and 

 teeth in the class Reptilia, as exem- 

 plified in existing forms, forbids the supposition that such a 

 structure as is implied by a power of mastication equal to that 

 enjoyed by the herbivorous mammalia, was associated with 

 reptilian organization. As we have already remarked, no 

 living reptiles can masticate their food ; the insects or vege- 

 tables on which they feed are seized by the tongue or teeth, 

 and swallowed whole ; so that a moveable covering to the 

 jaws, similar to the lips and Cheeks of the mammalia, is not 

 necessary, either for confining substances subjected to the 

 action of the teeth as organs of mastication, or for the purpose 

 of seizing or retaining their prey. The herbivorous reptiles 

 gnaw off the vegetables on which they subsist, but do not 

 chew them ; consequently their teeth, when worn by use, 



i "Philos. Trans." 1825. 



