OF THE IGUANODON, AND OTHER SAURIAN REMAINS. 141 
the country of which this colossal reptile appears to have been the principal inha- 
bitant. 
If, from the fossils hitherto discovered in the Wealden formation, any conclusions 
maybe drawn as to the relative numerical proportion of the different genera of Rep- 
tiles that once existed in the country from whence these strata were derived, the 
Iguanodon must have largely predominated. From a careful calculation, I may 
venture to state, that not less than seventy individuals, varying in age and magni- 
tude, from the reptile just burst from the egg, and but a few inches in length, to the 
possessor of the gigantic femur above described, have come under my examination 
during the last twenty years ; and more than thrice that number have, in all proba- 
bility, been destroyed by the workmen, and altogether eluded the observation of the 
palaeontologist. 
Saurian vertebras : undetermined . — Although it is my intention to restrict this notice 
to the remains of the Iguanodon and Hylaeosaurus, I cannot refrain from briefly 
alluding to some vertebrae which differ from any I have elsewhere observed. The 
first (Plate IX. fig. 6.) is a biconcave caudal vertebra, which, instead of having a de- 
pression, as in the Iguanodon, for articulation with the haemapophysis, has two tu- 
bercles ( ff ). The second is a caudal vertebra (Plate IX. fig. / .), in which the haema- 
pophysis consists of two distinct processes, which are anchylosed to the body of the 
vertebra, as in some of the caudal of the Mosaesaurus. 
A few vertebrae of the lacertian type, from five to six inches in length, have also 
been found ; these have the body convex posteriorly, and concave anteriorly (Plate IX. 
fig. 4.) ; and are wider than high , as in the Iguana and Monitor, and not in the reverse 
proportion, as in the Crocodile. One sacral vertebra (Plate IX. fig. 5.) closely resem- 
bles that of the Monitor. 
Hylaeosaurus, or IVealden Lizard . — I have discovered the remains of three indivi- 
duals of this genus in different localities in Tilgate Forest ; and these specimens, 
with the exception of a few detached bones found associated with relics of the 
Iguanodon, comprise all that is at present known of the osteology of this most extra- 
ordinary reptile. 
If the common observer be struck with astonishment at the colossal size and im- 
posing aspect of the bones of the Iguanodon, the comparative anatomist, who for the 
first time inspects the remains of the Hylaeosaurus, will not fail to experience equal 
surprise in the strange modifications of structure, and the blended osteological cha- 
racters, which these invaluable relics present to his notice. In the pectoral arch he 
will find an omoplate of the Crocodilian type united to a Lacertian coracoid ; in the 
ribs, the bilobed head of the Crocodile associated with the arched and rounded 
process of the Lizard, and an expansion of the bone at its spinal curvature so great, 
as to remind him of the peculiar condition of the costal apophyses of the Testudinata; 
while enormous osseous spines and plates demonstrate a dermal development, to 
which the existing reptiles afford but a slight analogy. The remark of Baron Cuvier 
u 2 
