OF THE IGUANODON, AND OTHER SAURIAN REMAINS. 
135 
Teeth of the Iguanodon. — Since my former memoir on the teeth of the Iguanodon, 
I have collected upwards of 250 specimens, of which 120 are deposited in the British 
Museum. They present every variety of condition, from that of a perfect tooth, 
with the fang extending to a point (as in Plate VII. figs. 1, 2.), to a mere stump, 
having the crown worn flat by use, and the fang absorbed by the pressure of the suc- 
cessional tooth. The largest tooth is 1 y^ths of an inch in width at the crown ; the 
smallest is a mere point (Plate VI. figs. 7,8.), and appears to have been a germ from 
the base of the fang of an old tooth. In almost every instance the apex of the crown 
is more or less worn. The specimen which presents the peculiar characters of the 
teeth in the greatest perfection, is that figured in Plate VI. figs. 1, 2, 3*. The pris- 
matic form of the crown, the serrated lateral margins, and the prominent longitu- 
dinal ridges are beautifully preserved. With a powerful lens, even the distribution 
and ramification of the vessels of the pulp, with the calcigerous tubes, forming a 
reticulated structure, as in the teeth of certain fishes, and, therefore, differing essen- 
tially in this respect from the teeth of the Iguana, may be distinctly seen through 
the delicate coat of enamel, presenting that peculiar arrangement which Professor 
Owen first pointed out to me as existing in the tooth of the Iguanodon, and which 
may be detected in polished sections by the aid of the microscope. On comparing 
the fang of this tooth, and of that figured, Plate VII. figs. 1, 2, with those of the 
Iguana (see magnified view, Plate V. fig. 4.), it will be seen that in the fossils the 
shank gradually tapers from the neck down to its inferior extremity ; while in the 
Iguana it is of a cylindrical form, and enlarges at the base in which the germ of the 
successional tooth (Plate V. fig. 4. h) is lodged. The worn state of the crown of the 
tooth, even in very young individuals, is well shown in the specimen, Plate VI. figs. 5, 
6, in which the absorption of the fang has proceeded with equal rapidity, scarcely any 
portion of it having remained (Plate VI. figs. 5, 6. b b). This condition of the tooth is so 
frequent, as to render it probable that in the Iguanodon the successional teeth advanced 
almost to the base of the crown before the attachment of the old teeth to the alveolar 
parapet was destroyed ; in the Iguana, on the contrary, the displaced tooth generally 
preserves some portion of the shank. In a few examples the crown is rounded, as in 
Plate VI. fig. 4 ; a form which may probably be attributable to an oblique position 
of the tooth in relation to its antagonist in the opposite jaw. But these modifications 
of form and structure, I leave to be fully elucidated by the accomplished palaeonto- 
logist (Mr. Owen), whose labours in Odontography are so deservedly appreciated. 
To convey an idea of the position of the teeth, and the proportionate magnitude of 
the jaw, a figure of two large teeth of the Iguanodon, in place, is annexed (Plate VII. 
figs. 6, 7 -)- The teeth are represented with great fidelity, and are characteristic of the 
state in which the largest and most perfect examples occur in the limestone of Tilgate 
Forest. A specimen with the apex unworn is figured in the same Plate, fig. 3. 
* This specimen has already been figured in several works, but the published figures are incorrect ; the an- 
nexed drawings have been executed with scrupulous accuracy. 
