THE IGUANODON AND HYL^OSAURUS. 
273 
more from their constant collocation with undoubted bones of that reptile, and the 
absence of any remains of the extremities of other species or genera to which they 
could have belonged, than from any legitimate anatomical deductions — yet almost 
all these bones have since been referred to distinct genera by Professor Owen*. 
Among the fossils lately obtained from the Isle of Wight, are certain cervical, an- 
terior and middle dorsal, and posterior caudal vertebrae, which so closely approxi- 
mate in their essential characters to the other elements of the spinal column of the 
Iguanodon, as to leave but little doubt that they belong to that animal. And 
although in the absence of any connected portions of the anterior part of the spine 
absolute certainty cannot be obtained, the close typical affinity of the bones in ques- 
tion supports this view of the subject, rather than that which assigns them to distinct 
genera of reptiles, of which no other less questionable vestiges have been discovered 
in the Wealden formation. 
I will now briefly state the result of a careful examination and comparison of all 
the materials to which we could obtain access ; the anatomical details, and the descrip- 
tion of the essential osteological characters upon which our opinions are based, have 
been drawn up by Dr. Melville, and his subjoined report will, I doubt not, be re- 
garded by the scientific palaeontologist as the most valuable part of this memoir. 
Cervical vertebrae, Plate XXVIII, figs. 4 , 6. — In my Geology of the South-East of 
England'l' (published in 1833 ), several large convexo-concave vertebrae from Tilgate 
Forest are described as presenting the true lacertian type, being concave anteriorly, 
and convex posteriorly, as in the Iguana, Monitor, Crocodile, &c., and this statement 
is repeated in my memoir of 1841 :}:. But Professor Owen, from a more accurate 
examination of one of these bones (now in the British Museum), in which the poste- 
rior oblique processes remain, discovered that the relative position of this vertebra 
in the skeleton must have been the reverse of that which I had assigned to it ; the 
convexity being anterior and the concavity posterior. A similar deviation from the 
ordinary Saurian structure had long since been detected by Cuvier in a fossil croco- 
dilian found at Honfleur, and figured and described in the “ Ossemens Fossiles" (tome v. 
p, 155 ) ; and which, though referred by Geoffroy to the genus Steneosaurus, has since 
been named by Von Meyer Streptospondylus (reversed spine) ; a most objectionable 
name, since the same character prevails in several fossil genera, as well as in many ex- 
isting Mammalia. The fossil vertebrae from Tilgate Forest, above mentioned, are as- 
signed by Professor Owen to the genus Streptospondylus of Von Meyer, as S. major 
But notwithstanding this decision, and the adoption of Professor Owen’s interpre- 
* See Reports on British Fossil Reptiles, vol. for 1841, pp. 88-94. f Page 307. 
t Philosophical Transactions, p. 141, PI. IX. fig. 4. 
§ British Association Reports, 1841, p. 91. The eminent author appears however to have entertained some 
doubts whether the appropriation was correct, and the vertebra in question .might not belong to his genus 
“ Cetiosaurus but he dismisses the suspicion with the remark, “ that the general constancy of the vertebrse 
of the same Saurian in their antero-posterior diameter forbids the supposition of a vertebra 6 inches in length 
in the neck, being associated with one 3 inches in length in the back,” p. 96. 
