inch from the inferior edge of the ramus. From the coronoid process, the height diminishes with a tolerably rapid sweep (but not so rapid as in Iguanodon), and the broken end, 2⋅5 inches from the articular surface, is only 0⋅5 inch high. The mandibular teeth are completely hidden.
The centrum of a vertebra (fig. 1, c), which lies on the outer side of the ramus of the mandible, is 0⋅6 inch long, and the exposed articular end, which is very slightly concave, is 0⋅45 inch high by 0⋅4 inch wide. The middle of the centrum is narrower than the ends, and the whole centrum, seen sideways, looks remarkably flat and wall-sided. Any processes the vertebra possessed must have come off from the neural arch, and therefore there can be no doubt that this is a dorsal vertebra. Thus the length of the skull appears to have equalled that of about six dorsal vertebræ.
The teeth of this reptile leave no doubt as to its distinctness from Iguanodon; and, as I shall immediately bring forward evidence to prove, that difference is generic. I propose, therefore, to name it Hypsilophodon[1] Foxii.
In the British Museum there is a considerable portion of the skeleton of a reptile, imbedded in the two portions of a slab of Wealden sandstone, of which the one was formerly the property of Dr. Mantell and the other of Dr. Bowerbank, but which are now happily reunited. This skeleton has been described and figured by Professor Owen, in the publications of the Palæontographical Society, as that of a young Iguanodon Mantelli.
The fossil is stated to have been discovered "in the Wealden formation, about one hundred yards west of Cowleaze Chine, on the north-west coast of the Isle of Wight, in the year 1849;" and the Rev. Mr. Fox informs me that it was found in the same bed as his specimen of Hypsilophodon, a stratum which, up to the present time, has yielded no remains of Iguanodon.
Two years ago, namely in December 1867, I became convinced, by the evidence of the British-Museum specimen itself, that it could not possibly be Iguanodon. The form and proportions of the vertebræ, especially of the caudal vertebræ, were quite different; the femur, with many points of similarity, exhibited sundry remarkable differences; and, most important of all, the metatarsus proved the Cowleaze reptile to have, at fewest, four well-developed toes. Again, if, as the describer of the fossil imagined, the bones numbered 66 and 67 (Palæontographical Society, "Fossil Reptilia of the Wealden," tab. i.) are the right tibia and fibula, any identification with Iguanodon is out of the question, inasmuch as the leg would be much longer than the femur, while in Iguanodon, as the Maidstone specimen proves, it is shorter. Thus I made sure that the Cowleaze fossil represented a new genus; and, under the circumstances, the probability that it once formed part of the body of a Hypsilophodon is obviously very great. The fortunate preservation of the centrum of a single dorsal vertebra, along with the skull, greatly strengthens this already strong presumption. On compari-
