Note 132 — SUPPLEMENTARY NOTES.

The following is the description of the specimens first discovered, given in the "Fossils of the South Downs; or, Illustrations of the Geology of Sussex," 1 vol. 4to. 1822: "Incisors and molar teeth evidently belonging to the same species of animal: they differ from any previously known; the masticating surface is perfectly smooth and rather depressed in the centre; these teeth consist of the crown only, and are quite solid. An incisor tooth 1.3 inch long Is slightly bowed and smooth on its inner surface; but it has externally a ridge which extends longitudinally down the front. Its sides are angular and the edges finely crenated." From the resemblance of these teeth in their general form to those of the Iguana, a common land lizard in the West Indies, I subsequently proposed the name of Iguanodon (implying an animal having teeth like the Iguana) for the fossil reptile. The teeth of an Iguana four or five feet long are not larger than those of a mouse; the Iguanodon's teeth are as large as the incisors of the rhinoceros. The Iguana's teeth, when used, are chipped off at the points, no existing reptile being capable of performing mastication; the teeth of the Iguanodon, on the contrary, are ground down like the worn molars of herbivorous mammalia, as I pointed out in my first memoir in the Philos. Trans. 1825.