n8 ANIMAL LIFE PAST AND PRESENT. 



the Iguanodons really walked on their hind legs like 

 birds ; but if we require further evidence on this point 

 it is ready to our hand. Far in the Wealden sand- 

 stones of Hastings there have been found numerous 

 series of impressions of huge three-toed hind feet, 

 corresponding exactly in size with the three-toed feet 

 of the Iguanodon ; and, since there are no impressions 

 of the smaller fore feet among these tracks, the bipedal 

 gait of the Iguanodon is proved from an independent 

 line of evidence. The three toes of the Iguanodon, 

 it may be observed, were terminated by broad and 

 flattened bones more like hoofs than claws, thus again 

 indicating the herbivorous nature of these reptiles. 



The description of the details in which the skeleton 

 of the Iguanodon approximates to that of birds would 

 involve too many abstruse anatomical points to be 

 given at full length in these pages, although we shall 

 have some observations to make on these points in 

 the latter part of the chapter. It may, however, be 

 observed in this place that all the bones of the limbs 

 were hollow, as in birds, while those of all living 

 reptiles are solid. Then the two long and rod-like 

 bones descending from the haunches behind the thigh- 

 bone are essentially bird-like in form and position, and 

 differ totally from the corresponding bones of crocodiles 

 and lizards. Again, the reduction of tliQ number of 

 hind toes to three, and the close relationship of the 

 upper bones of the ankle to those of the leg, are strong 

 points of resemblance to birds. It is true, indeed, 

 that in birds the three parallel long-bones of the foot 



