THE CRETACEOUS PERIOD. 287 



upon its hind-limbs, after the manner of a Bird. This conjec- 

 ture is further supported by the occurrence in the strata which 

 contain the bones of the Iguanodon of gigantic three-toed foot- 

 prints, disposed singly in a double track. These prints have 

 undoubtedly been produced by some animal walking on two 

 legs ; and they can hardly, with any probability, be ascribed to 

 any other than this enormous Reptile. Closely allied to the 



Fig. 210. Skull of Mosasaurus Camperi, greatly reduced. Maastricht Chalk. 



Iguanodon is the Hadrosaurus of the American Cretaceous, the 

 length of which is estimated at twenty-eight feet. Iguanodon 

 does not appear to have possessed any integumentary skeleton ; 

 but the great Hylaosaurus of the Wealden seems to have been 

 furnished with a longitudinal crest of large spines running 

 down the back, similar to that which is found in the compara- 

 tively small Iguanas of the present day. The Megalosaurus of 

 the Oolites continued to exist in the Cretaceous period; and, as 

 we have previously seen, it was carnivorous in its habits. The 

 American Lalaps was also carnivorous, and, like the Megalosaur, 

 which it very closely resembles, appears to have walked upon 

 its hind-legs, the fore-limbs being disproportionately small. 



Another remarkable group of Reptiles, exclusively confined 

 to the Cretaceous series, is that of the Mosasauroids, so called 



