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.