272 
DR. MANTELL ON THE OSTEOLOGY OF 
elusions as to the distinctive characters of the vertebrae belonging to different parts 
of the spine of the same species of fossil reptile — in which there is no clue to guide us 
through the labyrinth but analogy — I was so fortunate as to obtain the invaluable aid 
of that profound anatomist and physiologist, Dr, A. G. Melville, without whose co- 
operation it would have been impossible for me, from the pressure of professional 
engagements, to have instituted the requisite comparison of the specimens with the 
corresponding bones of allied recent and fossil species ; or to have arrived at the 
determination of the true place in the vertebral column of certain isolated vertebrae 
presenting remarkable dissimilarities in their characters, and which had formerly 
been assigned by myself and others to distinct genera of Saurians. 
As the present communication may be regarded as supplementary to my former 
attempts to illustrate the osteological structure of the Wealden reptiles, I propose, 
for the convenience of reference, to notice the various subjects under review, in the 
order adopted in my memoir published in the Philosophical Transactions for 1841. 
Iguanodon. Angular Bone of the Lower Jaw. — With the gigantic femora, tibiae, 
and vertebrae, hereafter described, were found'associated numerous fragments of large 
ribs, vertebral processes, &c., and a portion of a long arched bone of so peculiar a 
shape as to defy all my attempts to determine its place in the skeleton, till the saga- 
city of Mr. Waterhouse (of the British Museum) recognized its accordance with the 
angular bone of a reptile ; an opinion which a careful comparison of the fossil with 
recent types has satisfactorily confirmed. The specimen is 10 inches in length, and 
proves to be the right angular bone of the lower jaw of a large Iguanodon ; it exhibits 
the deep longitudinal channel, and the post-opercular notch, peculiar to that maxil- 
lary element in Saurians, but is not sufficiently perfect to afford an instructive deline- 
ation ; the length of the jaw to which it belonged was probably from 3 to 4 feet. 
Vertebral Column. — The structure of the middle dorsal and anterior caudal vertebrae, 
was first established by the figures and descriptions given in my various geological 
works, and by the references to these parts of the skeleton in the Maidstone speci- 
men ; for although the vertebrae in that celebrated fossil are more or less distorted 
by compression, their distinctive characters are not obliterated, but may be recog- 
nized by due attention. 
The elaborate and critical examination of all the Saurian vertebrae from the 
Wealden collected by myself and others, given in the masterly reports on the British 
Fossil Reptiles by Professor Owen, undertaken and published at the expense of the 
British Association of Science since the appearance of my memoir in the Philoso- 
phical Transactions for 1841, has supplied many important diagnostic details of 
great value to the cultivator of this department of palaeontology. But the deter- 
mination of the cervical, anterior dorsal, lumbar, and terminal caudal, has not 
hitherto been satisfactorily accomplished. For although in my earlier attempts to 
interpret the mutilated and generally isolated relics of gigantic Saurian skeletons 
which were from time to time exhumed in the Wealds of the south-east of England, 
certain large vertebrije of dissimilar forms were vaguely assigned to the Iguanodon — 
