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HISTORICAL PALAEONTOLOGY. 



lived principally on the foliage of the Cretaceou-s forests 

 amongst which it dwelt. Its size has been variously estimated 



Fig. 209. — Teeth o{ Iguanodott Mantellii. Wealden, Britain. 



at from thirty to fifty feet, the thigh-bone in large examples 

 measuring nearly five feet in length, with a circumference of 

 twenty-two inches in its smallest part. With the strong and 

 massive hind-limbs are associated comparatively weak and 

 small fore-limbs ; and there seems little reason to doubt that 

 the Iguanodon must have walked temporarily or permanently 

 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 smgly 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 

 Iguanodoji is the Hadrosaiirus 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 Hylceosaiiriis of the Wealden seems to have been 

 furnished with a longitudinal crest of large spines running 

 do^\^l the back, similar to that which is found in the compara- 

 tively small Iguanas of the present day. The Megalosaiirus of 

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

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

 American I^la^s was also carnivorous, and, like the Megalosaur, 



