seems to me that we
should turn to the facts we have in our possession for the explanation
of these mysterious footprints, rather than endeavor to supply by
assumption those which we have not. As there are no bones found in
connection with these tracks, the only way to arrive at their true
character, in the present state of our knowledge, is by comparing them
with bones found in other localities in the deposits of the same period
in the world's history. Now there have never been found in the Trias any
remains of Birds, while it contains innumerable bones of Reptiles; and
therefore I think that it is in the latter class that we shall
eventually find the solution of this mystery.

[Footnote 10: For all details respecting these tracks see Hitchcock's
_Ichnology of New England_. Boston, 1858. 4to.]

It is true that the bones of the Triassic Reptiles are scattered and
disconnected; no complete skeleton has yet been discovered, nor has any
foot been found; so that no direct comparison can be made with the
steps. It is, however, my belief, from all we know of the character of
the Animal Kingdom in those days, that these animals were reptilian, but
combined, like so many of the early types, characters of their own class
with those of higher animals yet to come. It seems to me probable, that,
in those tracks where one toe is turned backward, the impression is made
not by a toe, but by a heel, or by a long sole projecting backward; for
it is not pointed, like those of the front toes, but is blunt. It is
true that there is a division of joints in the toes, which seems in
favor of the idea that they were those of Birds; for when the three toes
are turned forward, there are two joints on the inner one, three on the
middle, and four on the outer one, as in Birds. But this feature is not
peculiar to Birds; it is found in Turtles also. The correspondence of
these footprints with each other leaves no doubt that they were all by
one kind of animal; for both the bipedal and the quadrupedal tracks have
the same character. The only quadrupedal animals now known to us which
walk on two legs are the Kangaroos. They raise themselves on their hind
legs, using the front ones to bring their food to their mouth. They leap
with the hind legs, sometimes bringing down their front feet to steady
themselves after the spring, and making use also of their tails, to
balance the body after leaping. In these tracks we find traces of a tail
between the fee