ROOM III. PHYSIOLOGICAL INFERENCES. 309 



and nerves that supplied the front of the mouth, indicate the 

 great development of the integuments and soft parts, with 

 which the lower jaw was invested. 



The sharp ridge bordering the deep groove of the sym- 

 physis, in which there are also several foramina, evidently 

 gave attachment to the muscles and integuments of the 

 under lip ; while two deep pits for the insertion of the pro- 

 tractor muscles of the tongue, manifest the mobility and 

 power of that organ. There are therefore strong reasons for 

 supposing that the lip was flexible, and, in conjunction with 

 the long fleshy prehensile tongue, constituted the instruments 

 for seizing and cropping the leaves and branches, which, from 

 the construction of the molars, we may infer constituted the 

 chief food of the Iguanodon. The mechanism of the maxil- 

 lary organs, as elucidated by recent discoveries, is thus in 

 perfect harmony with the remarkable characters w T hich ren- 

 dered the first known teeth so enigmatical ; and in the Wealden 

 herbivorous reptile we have a solution of the problem, how 

 the integrity of the type of organization peculiar to the class 

 of cold-blooded vertebrata was maintained, and yet adapted, 

 by simple modifications, to fulfil the conditions required by 

 the economy of a gigantic terrestrial reptile, destined to ob- 

 tain support exclusively from vegetable substances; in like 

 manner as the extinct colossal herbivorous Edentata which 

 flourished in South America, ages after the Country of 

 the Iguanodon and its inhabitants had been swept from the 

 face of the earth. 



Thus in the unlimited production of successional teeth at 

 every period of the animal's existence, in the mode of im- 

 plantation of the teeth, and in the composite structure of the 

 lower jaw, each ramus consisting of six distinct elements, 

 the saurian type of organization is unequivocally manifest; 

 while the intimate structure of the dental organs approaches 

 that of the Sloths, and the subalternate arrangement and 

 reversed position of the upper and lower series of teeth 

 corresponds with that of the Ruminants. And again, the 

 edentulous and prolonged symphysis, and the great develop- 

 ment of the lower lip and the integuments of the jaws, as 

 indicated by the size and number of the vascular foramina, 

 present a striking analogy to the Edentata. They who doubt 

 the correctness of this interpretation, should remember that 



