One of the most celebrated of the Cretaceous Deinosaurs
is the _Iguanodon_, so called from the curious resemblance of
its teeth to those of the existing but comparatively diminutive
_Iguana_. The teeth (fig. 209) are soldered to the inner face
of the jaw, instead of being sunk in distinct sockets; and they
have the form of somewhat flattened prisms, longitudinally ridged
on the outer surface, with an obtusely triangular crown, and
having the enamel crenated on one or both sides. They present
the extraordinary feature that the crowns became worn down flat
by mastication, showing that the _Iguanodon_ employed its teeth
in actually chewing and triturating the vegetable matter on which
it fed. There can therefore be no doubt but that the _Iguanodon_,
in spite of its immense bulk, was an herbivorous Reptile, and lived
principally on the foliage of the Cretaceous forests amongst which
it dwelt. Its size has been variously estimated at from thirty to
fifty feet, the thigh-bone in large examples measuring nearly
five feet in length, with a circumference of twenty-two inches
in its smallest part. With the strong and massive hind-limbs are
associated comparatively weak and small fore-limbs; and there
seems little reason to doubt that the _Iguanodon_ must have walked
temporarily or permanently upon its hind-limbs, after the manner of
a Bird.
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