WEALDEN FORMATIONS. 7 



The ungual phalanx (iv 5) is relatively more slender than in the inner toe : its 

 length is 4 inches ; its basal breadth 1 inch 10 lines. The obliquity of the bone is 

 slight, and in the opposite direction to that of the inner toe. 



Should any rudimental or spurious claw have been supported by the raetapodial of 

 the innermost digit (T. II, fig. 2, i), the development of which toe is so remarkably 

 arrested, it would probably present that form, and in regard to the fully grown 

 Iguanodon, that size, which characterises the claw-phalanx which has been mistaken 

 for the "horn" of the Iguanodon. It is probable that, in the fore-foot, the toe 

 answering to the innermost in the Iguana's foot was better developed than its homotype 

 in the hind-foot. 



Not far from where the foot-bones were found, the femur, tibia, and fibula, of the 

 same Iguanodon were extracted, — a circumstance which adds to the probability of 

 their belonging to the same limb. 



The modification of the present foot, whether of the fore- or hind-limb, of the 

 Iguanodon is unique, according to present knowledge, in the class Reptilia. It 

 exhibits an adaptation to terrestrial progression, and the support of a weighty super- 

 incumbent trunk, akin to that which we observe in the tridactyle foot of the heavy 

 perissodactyle Pachyderms, represented at the present day by the Rhinoceros and 

 Tapir. 



