The occurrence of fossils of this nature in the strata forming the districts denominated the Wealds of Sussex and Kent, was first brought under the notice of geologists in 1822, in my work on the "Fossils of the South Downs," in which the remains of several unknown reptiles were described; and among them the teeth and bones of that extraordinary herbivorous lizard, the _Iguanodon_, on which I am induced to offer a few observations in this place; the recent discovery of some previously undetermined parts of the skeleton, having materially elucidated the structure and economy of the original.[132] [Footnote 132: 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.] Since the first announcement of the discovery of the remains of the Iguanodon, vast quantities of bones belonging to a great number of individuals of all ages have been collected; but until a few years since, not a vestige of the jaws had been observed, notwithstanding the most diligent research. In the early part of the year 1848, I was surprised and highly gratified by receiving from Capt. Lambart Brickenden (at that time a personal stranger to me), who then resided at Warminglid, near Cuckfield, in Sussex, the greater part of the right side (or _ramus_) of the lower jaw, with several successional teeth in their natural position, of an adult Iguanodon.[133] See p. 202. [Footnote 133: This beautiful and most instructive specimen is now in my possession; it is figured of the natural size in Philos. Trans. Part ii. for 1848, Plate XVI., as well as the portion of upper jaw in the British Museum, Plate XIX. The character of the upper and lower teeth of the Iguanodon are well represented in Plate XVIII. of the same memoir.