54 FOSSIL REPTILTA OF THE WEALDEN FORMATIONS. 



resembled the Iguana in the length of its tail,* as in the anatomical characters 

 of any of the constituent vertebrae of that part : the changes which the series of six 

 caudal vertebrae present in the length and form of the spinous processes, and in the 

 place of origin of the transverse processes, indicate the tail to have been relatively shorter 

 in the Iguanodon than in the Crocodile. Assuming, however, that the number of caudal 

 vertebrae of the Iguanodon equalled that in the Crocodile, and allowing to each vertebra 

 with its intervertebral space A\ inches, we obtain the length of 12 feet 6 inches for 

 the tail of the Iguanodon. On the foregoing data, therefore, we may liberally assign 

 the following dimensions fo the largest Iguanodon : 



Feet. 

 Length of head, say . . .3 



Length of trunk with sacrum . .12 



Length of tail . . . .13 



Total length of the Iguanodon . 28 



The same observations on the general form and proportions of the animal, and its 

 approximation in this respect to the Mammalia, especially the great extinct Megatherioid 

 or Pachydermal species, apply as well to the Iguanodon as to the Megalosaurus. 



* See also the judicious remarks by Dr. Buckland to the same effect, ' Bridgewater Treatise,' p. 244. 



