280 
IGUANODON 
are, at least, twenty times larger than those of the 
Iguana ; that the thigh-bone is of equally enormous 
proportions : and were we to calculate the probable 
magnitude of the original, from the data which this 
metatarsal bone affords, our readers might well 
exclaim, that the realities of Geology far exceed 
the fictions of romance. Even if we admit, what 
is, indeed, probable, that the linear dimensions of 
the extinct and living animals were not of the same 
relative proportions, still it must be allowed that 
the Iguanodon was one of the most gigantic reptiles 
of the ancient world ; and a colossus in comparison 
to the pigmy alligators and crocodiles that now 
inhabit the globe. 
Horn of the Iguanodon We have now to re- 
quest the attention of the reader to a very remark- 
able appendage, with which there is eveiy reason to 
believe the Iguanodon was provided. This is no 
less than a /mm, equal in size, and not very dif- 
ferent in form, to the lesser horn of the Rhinoceros. 
This unique relic is externally of a dark brown 
colour ; and while some parts of its surface are 
smooth, others are rugose and furrowed, as if by 
the passage of blood-vessels. Its base is of an 
irregular oval form, and slightly concave. It pos- 
sesses an osseous structure, and appears to have no 
internal cavity. It is evident that it was not united 
to the skull by a bony union, as are tlie horns of 
the mammalia. The nature of this extraordinary 
fossil was for some time undetermined ; and it is to 
the discrimination of Mr. Pentland, whose higli at- 
tainments in com])arative anatomy are well known, 
that we are indebted for the suggestion that it pro- 
