184 Mr. Mantell on the iguanodon^ 
dentated ; the outer surface is ridged, and the inner smooth 
and convex ; and as in that animal the secondary teeth appear 
to have been formed in a hollow in the base of the primary 
4 
ones, which they expelled as they increased in size. From the 
appearance of the fangs in such fossil teeth as are in a good 
state of preservation, it seems probable that they adhered to 
the inner side of the maxillae, as in the iguana, and were not 
placed in separate alveoli, as in the crocodile. The teeth ap- 
pear to have been hollow in the young animals, and to have 
become solid in the adult. The curved teeth (figs, i, 2.) 
probably occupied the front of the jaw ; and those which are 
nearly straight, (fig. 3.) the posterior part. 
It appears unnecessary to dwell longer on the resemblance 
existing between the recent and fossil teeth. Whether the 
animal to which the latter belonged, should be considered as 
referable to existing genera, differing in its specific characters 
only ; or should be placed in the division of enalio-sauri of 
Mr. CoNYBEARE, which includes marine genera only, cannot 
at present be determined. If however any inference .may 
be drawn from the nature of the fossils with which its re- 
mains associated, we may conclude, that if amphibious, it 
was not of marine origin, but inhabited rivers or fresh- water 
lakes ; in either case the term Iguanodon, derived from the 
form of the teeth, (and which I have adopted at the sugges- 
tion of the Rev. W. Conybeare) will not, it is presumed, be 
deemed objectionable. 
It has already been mentioned, that of the bones of ovipa- 
rous quadrupeds found in the sandstone ofTilgate forest, 
some are decidedly referable to the crocodile, and others to 
the megalosaurus and iguanodon ; but our knowledge of the 
