proved highly satisfactory, for in an Iguana which Mr. Stutchhury had
prepared to present to the College, we discovered teeth possessing the
torm and structure of the fossil specimens.
“ Like the teeth of the recent Iguana, the crown of the tooth is
acuminated; the edges are strongly serrated or dentated ; the outer
surface is ndged, and the inner smooth and convex; and, as in that
animal the secondary teeth appear to have been formed in a hollow
m the base of the primary ones which they m size. expelled as they increased
From the appearance of the fangs in such fossil teeth as are
1 a g °0d stateof preservation, it seems probable that they adhered to
e inner side of the maxillm, as in the Iguanas, and were not placed
m separate alveoli, as m the crocodile. The teeth appear to have
een hollow m the young animals, and to have become solid in the
adult, fhe curved teeth probably occupied the front of the jaw ■ and
those which are nearly straight the posterior part.” (1)
A subsequent discovery by Dr. Mantell(2) of a portion of the
lower jaw of the Iguanodon confirmed the previous inference as to
the mode of attachment of the teeth, and approximates the extinct
gigantic species to the Pleurodont section of Iguanians; whence it
may also be inferred that the teeth were all of nearly uniform size
and shape at least not divisible into laniaries and molars as in the
Theporlion of jaw alluded to, which is now in the British Museum
with the rest of the Mantellian Collection, shows that the feuanodon
differed from the Crocodile not only in the lateral adhesion of the
teeth to an alveolar wall, but in their arrangement in a close-set senes.B
esides the opportunity of studying this unique fossil and the
extensive series of detached teeth in the British Museum I have
availed myself of the kindness of Dr. Mantell and Mr Dixon of
Worthing to examine the specimens in their private collections and
I have been favoured by both these gentlemen with Iguanodon’s ’teeth
from which I have had sections prepared for microscopical examination.
(1) Philos. Trans. 1825, Mr. Mantell, Notice on the Iguanodon.
(2) Wonders of Geology, vol. 1, p, 393
The teeth of the Iguanodon, though resembling most closely
those of the Iguana, do not present an exact magnified image of
them, but differ in the greater relative thickness of the crown, its
more complicated external surface, and, still more essentially in a
modification of the internal structure, by which the Iguanodon equally
deviates from every other known reptile.
As in the Iguana, the base of the tooth is elongated, contracted
and suhcylindrical; the crown expanded, and smoothly convex on the
inner side ; when first formed (PI. 70, fig. 5) it is acuminated, compressed,
its sloping sides serrated, and its external surface traversed
by a median longitudinal ridge, and coated by a layer of enamel, but
beyond this point the description of the tooth of the Iguanodon indicates
characters peculiar to that genus. In most of the teeth that
have hitherto been found, three longitudinal ridges traverse the outer
surface of the crown, one on each side of the median primitive ridge ;
these are separated from each other and from the serrated margins of
the crown by four wide and smooth longitudinal grooves. The relative
width of these grooves varies in different teeth; sometimes a
fourth small longitudinal ridge is developed on the outer side of the
crown as in the small anterior Iguanodon’s tooth in Plate 62 a ,
fig. 5, a.
The marginal serrations, which, at first sight, appear to he
simple notches, as in the Iguana, present under a low magnifying
power the form of transverse ridges, themselves notched, as shown in
PI. 62 a ., fig. 5 e.(l) so as to resemble the mammillated margins of
the unworn plates of the elephant’s grinder : slight grooves lead from
the interspaces of these notches upon the sides of the marginal ridges.
These ridges or dentations do not extend beyond the expanded part of
the crown : the longitudinal ridges are continued farther down, especially
the median ones which do not subside till the fang of the tooth
begins to assume its suhcylindrical form.
■ The tooth at first increases both in breadth and thickness; it then
diminishes in breadth, but its thickness goes on increasing (as shown
, (1) This figure, and those numbered 5, 6, 8, 9 and 10, PI. 62 A., are zincographed from
drawings by Mr. Dinkel kindly communicated to me by Dr. Mantell for the present work.