THE IGUANODON AND HYL^OSAURUS. 
285 
and correctly assigned, and the true characters of the vertebral column demon- 
strated, so far as the data hitherto obtained afford the means of re-connecting its dis- 
jointed elements. 
The physiological inferences resulting from this investigation confirm, in every 
essential particular, those which I had the honour to submit to the Society in my 
late memoir on the maxillary and dental organs of the Iguanodon. By the deter- 
mination of the principal bone of the arm, we now discover that the fore-limbs of 
the colossal original were more reptilian in their relative proportions with other parts 
of the skeleton, than could a priori have been surmised. But this comparatively 
feeble development of the anterior extremities tends to confirm the opinion which I 
formerly advanced, that the fore-feet were long and slender, and served as prehensile 
instruments ; while the hinder limbs and feet were strong and massive, as in the 
Hippopotamus. 
Thus, after the lapse of more than a quarter of a century, I conclude my attempts 
to restore the skeleton of the gigantic Saurian, of whose former existence a few 
isolated and water-worn teeth were the sole known indications, when, in 1825, I 
ventured to communicate to the Royal Society, through my friend the late Davies 
Gilbert, Esq., P.R.S., “A Notice of the Teeth of an unknown Herbivorous Reptile 
discovered in the Strata of Tilgate Forest in Sussex.” 
19 Chester Square, Pimlico, 
\bth January, 1849. 
Notes on the V nrtebral Column of the Iguanodon. 
By A. G. Melville, M.D., Edin. M.R.C.S. 
The atlas and axis of this gigantic reptile have not hitherto been discovered, but 
we may expect, as in the corresponding vertebrae referred to the Steneosaurus rostro- 
minor (G. St. Hilaire), the pleural complement of the axis to have a double attach- 
ment, above to the superior transverse process derived from the base of the neural 
lamina, and below to an exogenous tubercle — inferior transverse process — on the 
lower part of the centrum of the atlas, or in addition, to the contiguous portion of 
the axis. In the recent Crocodiles, the cervical rib of the axis is displaced from its 
own centrum, and has an upper and lower attachment to the odontoid process or 
true centrum of the atlas. It will be a matter of great interest to ascertain if in any of 
the extinct Crocodilidse or Dinosauria, the rib-like processes of the atlas are attached 
to their proper centrum, and not displaced forwards on the heemal element of the 
occipital vertebra, or so-called body of the atlas, as in the existing Crocodiles ; a dis- 
placement which repeats the normal attachment of the ribs in fishes to the inferior 
or haemal elements of the bodies of the vertebrae. 
2 p 
MDCCCXLIX. 
