Year: 1861

"...... We will conclude our sketch Of the
principal meozoic sauriaas by brief notice of
two land lizards of enormous size-the Mega


tosaurus, which was originally discovered in
Stonefeld slate near Oxford and the Iguauo-
don found by the late DR.. Mantell, in the
Wealden formation of Tilgate Forest in Sussex.


The former of these creatures was carnlyorous,
and attained the length of forty or fifty feet
The latter even reached seventy, but was her,
bevorous. The head of the Megelosaurus ter
minated in straight and narrow snout, armed
with teeth of the most formidable character,
combining the properties of the knife, The sword
and the saw. When first protruded from the
gum, the apex of each tooth presented double
sword-edge of serrated enamel but as the
tooth advanced in age, it took curve back
ward, like a pruning knife, the saw-ike edge
being continued on the cOncave side OF the very
root, while the convex side became blunt and
thick, just as a cuter makes tie back Of 4
knifeblade thicker for the purpose ofincreasing
its strength and steadiness = the backward
curvature OF the teeth, Of course, acting as a
harb, eflectualy preventing the escape of all
animals once seized in the jaws. The diet of
this creature appears to have consisted of the
smaller saurines, whose remains abound in the
same strata with its bones and the piercing.
crushing powers of its dental apparatus must
have been equal to dispose even Of veteran
crocodile. The Iguanodon appears TO have
been closely connected with its living congener,
the Iguana, an inhabitant Of the warm regions
of America. The conformation Of the teeth is
nearly identical in both, and both were distn-
guished by horn or bone upon their nose
But the living Iguana, which does not exceed
the length of five feet lives chiefly in trees,
feeding on fruit, seeds, and leaves. although
the female from time to time visits the water
for the purpose of laying her eggs in the sand,
But climbing trees was of course out of the
question for a monstrous creature of probably
seventy feet in length, and with limbs far ex-
ceedirg in bulk those of the largest elephant
for an existing thigh bone is, in its smallest
part, twenty-five inches round, and must have
been when perfect between four and five feet
long. Yet, the dental arrangement being the
same in the fossil and the living animal, the
nature Of the food must have been the same
for both and, accordingly, we must suppose
that the Iguanodon reared itself up against
the trees which were its cotemporaries-h
palms and tree-lerns-and despoiled them Of
the coarse, rough tops, which no teeth less eff
fective than its own could have masticated.-
This suppostion is confirmed by the massive
ness of the hinder limbs, and the shortness and
thickness of the tall as compared with that of
the Iguana. But the great peeuliarity Of both
these creatures is the shape OF their tecth
which may be compared to the pinccrs used
in cutting iron wire, with simple but ehectu
al provision for the continual maintenance Of
sharp cutting edge This is thin plate of
enamel, placed only on the fore part of the
tooth, as in the incisors Of the rat. The softer
material wearing away more rapidly in proper
tion to its distance from the enamel, an oblique
section of the crown Of tooth is constantly
preserved, with a keen edge in front.