ROOM III. PHYSIOLOGICAL INFERENCES. 311 



The size of the largest Iguanodon has been estimated as 

 follows : ! length of the head, three feet of the trunk, twelve 

 feet of the tail, thirteen feet total length, twenty-eight feet. 



This statement will surprise the reader who, from the 

 popular notions of the magnitude of the Iguanodon, has 

 entertained the idea that this reptile attained seventy feet in 

 length ; but the discrepancy between the above estimate and 

 that first suggested by me, admits of an easy explanation. 



In my earliest notices of the Iguanodon, which were pub- 

 lished from time to time, as fresh discoveries disclosed new 

 modifications of structure in this prodigious creature, an 

 attempt was made to estimate the probable magnitude of the 

 original, by instituting a comparison between the fossil bones 

 and those of the Iguana; the recent type which the form of 

 the teeth seemed to point out as the one most nearly related 

 to the extinct reptile. It was thus shown that if the propor- 

 tions were the same in both, the Iguanodon must have at- 

 tained seventy feet or more in length. But this statement 

 was qualified (more than eleven years since) by the remark 

 "It is not, of course, pretended that such an estimate can 

 offer more than a very distant approximation to the truth ; 

 yet it may be confidently affirmed that a reptile, which re- 

 quired a thigh-bone larger than that of the Elephant to sup- 

 port it, could not be of less colossal dimensions. In truth, 

 I believe that its magnitude is here underrated, for, like 

 Frankenstein, I was struck with astonishment at the monster 

 which my investigations had, as it were, called into existence, 

 and was more anxious to reduce its proportions than to exag- 

 gerate them. Should subsequent discoveries prove that the 

 Iguanodon more nearly corresponded in the proportions of 

 the tail with the Crocodilian family than with the Lizards, its 

 total length would be much less than is here inferred ; and 

 from the shape of some of the metacarpals and phalangeals, it 

 seems highly probable chat the original was more bulky in 

 proportion to its length, than the existing Lacertians." 



In subsequent notices this opinion was reiterated, and on 

 the discovery of several perfect anterior caudals, I expressed 

 my conviction that the tail of the Iguanodon was shorter 

 than in the Iguana, and instead of being long and round, was 



1 " Brit. Kep." 1841, p. 144. 



