1869. ] HUXLEY—HYPSILOPHODON. 7 
inch from the inferior edge of the ramus. From the coronoid pro- 
cess, the height diminishes with a tolerably rapid sweep (but not 
so rapid as in Zguanodon), 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, ¢), 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 vertebre. 
The teeth of this reptile leave no doubt as to its distinctness _ 
from Jquanodon ; and, as I shall immediately bring forward evidence 
to prove, that difference is generic. I propose, therefore, to name it 
Hypsilophodon* Foxit. 
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 Paleeontographical Society, 
as that of a young Jguanodon 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 Rey. 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 [quanodon. 
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 Jguanodon. The form and proportions of the ver- 
tebree, especially of the caudal vertebrae, were quite different ; the 
femur, with many points of similarity, exhibited sundry remark- 
able 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 (Palontographical Society, “Fossil Reptilia of the 
Wealden,” tab. i.) are the right tibia and fibula, any identification 
with Jguanodon is out of the question, inasmuch as the leg would 
be much longer than the femur, while in Jguanodon, as the Maid- 
stone specimen proves, it is shorter. Thus I made sure that the 
Cowleaze fossil represented a new genus; and, under the cireum- 
stances, 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- 
* Hypsilophus is a name proposed by Fitzinger for certain Iguanas. 
