Dr. Mantell, from the examination of the anterior part of the right
side of the lower jaw of an Iguanodon discovered in a quarry in Tilgate
Forest, Sussex, has detected an extraordinary deviation from all
known types of reptilian organisation, and which could not have been
predicated; namely, that this colossal reptile, which equalled in bulk
the gigantic Edentata of South America, and like them was destined to
obtain support from comminuted vegetable substances, was also furnished
with a large prehensile tongue and fleshy lips, to serve as instruments
for seizing and cropping the foliage and branches of trees; while
the arrangement of the teeth as in the ruminants, and their internal
structure, which resembles that of the molars of the sloth tribe in the
vascularity of the dentine, indicate adaptations for the same purpose.
Among the physiological phenomena revealed by paleontology, there
is not a more remarkable one than this modification of the type of
organisation peculiar to the class of reptiles to meet the conditions
required by the economy of a lizard placed under similar physical
relations; and destined to effect the same general purpose in the
scheme of nature as the colossal Edentata of former ages and the large
herbivorous mammalia of our own times.