also its type in the South of
Europe in the skink (_Scincus_), which was formerly supposed to possess
much medicinal value. This large family contains a number of species
which exhibit a series of gradations in structure leading to forms which
have the external aspect of serpents. One such form is the perfectly
harmless slow-worm, or blind-worm, of our own country, which in spite of
its scientific name, _Anguis fragilis_[14], is a legless lizard, and no
snake.

Other lizards of a very different kind forming the family _Amphisbaeidae_
are also legless, with the single exception of the genus _Chirotes_,
which has a pair of anterior limbs, but no posterior ones. The name of
this family is derived from the similarity of appearance presented by
both ends of the body, so that either end looks as if ready to take the
lead as "head."

A family of lizards familiar by name to us all from our childhood is the
family of chameleons (_Chameleonidae_). There are many species of
chameleons, but they are found in the Old World only; they are among the
most exceptional and peculiar of all lizards, but there is one form
which is yet more so.

This most exceptional of lizards is one found in New Zealand, and named
_Sphenodon_. Its external aspect would not lead the ordinary observer at
all to suspect that it is so remarkable a creature as its anatomy shows
it really to be.

The order _Crocodilia_ contains, of course, the true crocodiles which
are found both in the Old and New Worlds. It contains besides the
alligators (which are peculiar to America), as well as the long and
slender-snouted gavials which are now found only in India and Australia.
At one time the number of kinds of this order was very much greater than
at present, and interesting structural modifications have taken place in
it during the course of ages, as will be pointed out later.

On the whole, the order of crocodiles makes a much nearer approach to
mammals and birds--especially (strange as it may seem) to birds, than is
made by any other group of existing reptiles.

Reptiles, however, once existed have left their remains fossilized (in
the rocks of what is termed the "secondary" or "mesozoic" period), which
reptiles in the structure of their skeleton approach much more closely
to birds, and especially to birds of the ostrich order, than crocodiles
do. Amongst these reptiles may be mentioned the huge Iguanododon (type
of the, extinct order _Dinosauria_), which once