278 HISTORICAL PALAZONTOLOGY. 
lived principally on the foliage of the Cretaceous forests 
amongst which it dwelt. Its size has been variously estimated 
Fig. 209.—Teeth of 7ewanodon Mantelliz. 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 Lgwanodon 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 Zewanodon of gigantic three-toed foot- 
prints, disposed szzgZy 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 
Lguanodon is the Hadrosaurus of the American Cretaceous, the 
length of which is estimated at twenty-eight feet. Jgwanodon 
does not appear to have possessed any integumentary skeleton; 
but the great /Zy/eosaurus of the Wealden seems to have been 
furnished with a longitudinal crest of large spines running 
down the back, Srviler to that which is founee in the compara- 
tively small Iguanas of the present day. The AZegalosaurus of 
the Oolites continued to exist in the Cretaceous period ; and, as 
we have previously seen, it was carnivorous in its habits. The 
American Ze/aps was also carnivorous, and, like the Megalosaur, 
