Introductory .—The primary object of this communication is to bring to the notice of the Society numerous remains of an apparently new Iguanodont Reptile obtained by Mr. C. Dawson, F.G.S., of St. Leonards, from the Wadhurst Clay (one of the beds of the Hastings Sand, or lower division of the Wealden), and recently acquired by the British Museum; and also a maxilla from the Wealden of the Isle of Wight, apparently referable to Ornithopsis . Having, however, recently examined the whole of the collection of Dinosaurian remains preserved in the Museum, in the course of the preparation of the first part of the forthcoming ‘Catalogue of Fossil Reptilia’ of the collection, I have also made certain observations regarding other members of the order, which may be conveniently recorded at the same time. Iguanodonts .—Commencing with the Iguanodonts, I may first of all observe that I fully concur in the view which M. Dollo informs me he now takes as to the specific identity of Iguanodon bernissartensis and I. Seelyi ; and, although the original description is very meagre and unaccompanied by a figure, I think we ought to adopt the former and earlier name for the species which has been so well described by the Belgian naturalist. The British Museum possesses a considerable series of the remains of this species, many of which were referred by Sir R. Owen to Cetiosaurus and Pelorosaurus , while others have been described under the name of Iguanodon Mantelli . In addition to the two Wealden species of Iguanodon ( I.