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XIII. On the Structure of the Jaws and Teeth of the Iguanodon. 
By Gideon Algernon Mantell, Esq., LL.D., 
F.R.S., F.L.S., Vice-President of the Geological Society, Sfc. 
Received May 25, — Read May 25, 1848. 
In the deltas and estuaries of rivers that are of great extent, and which flow through 
countries of varied geological structure, we naturally expect to find the remains of 
terrestrial vertebrated animals that have been transported by the currents from far-dis- 
tant lands, in a more or less mutilated state ; the skeletons broken up — the bones dis- 
severed, fractured, and waterworn — the teeth detached from the jaws and dispersed — 
and all these separated parts promiscuously imbedded in the mud, silt, and sand of 
the delta, and intermingled with the debris of the flora of the country, and the 
durable remains of fishes, mollusks, and crustaceans, that inhabited the freshwater, or 
were denizens of the adjacent sea. Such is the condition in which the bones and 
teeth of oviparous quadrupeds are found in the Wealden formation of the south-east 
of England ; and hence the difficulty of obtaining satisfactory evidence of the form 
and structure of the extinct reptiles whose relics are so abundant in some of these 
deposits. 
I’o this cause may be ascribed the remarkable fact, that although several hundred 
teeth, belonging to seven or eight genera of Saurians, have been collected from these 
fluviatile strata, scarcely a portion of the cranium, and but a few fragments of the 
jaws, have been discovered. Every relic of this kind is consequently in the highest 
degree interesting, and it is therefore most gratifying to me to have it in my power 
to lay before the Royal Society a considerable portion of the lower jaw, with teeth, 
of an Iguanodon, recently obtained from a quarry near Cuckfield in Sussex ; the 
locality in which, nearly thirty years since, I first discovered the teeth of this colossal 
herbivorous Lizard. 
In the communication which I had the honour to address to this Society in 1841 *, 
a fragment of the lower jaw of a Saurian was described as that of a young Iguano- 
don, and the anatomical considerations which led me to offer that interpretation 
were fully detailed. But although from the form and mode of implantation of the 
fangs of the mature teeth, and the position of the germs of the successional ones, this 
inference appeared to be highly probable, yet as none of the crowns of the teeth 
remained, the peculiar dental characters of the Iguanodon were absent, and the pre- 
sumed generic identity could not be unequivocally established ; since it was possible 
* Philosophical Transactions, Part II. p. 131. 
