a bird and like a reptile. There is a long tail composed of many
vertebræ. The structure of the wing differs in some very remarkable
respects from that which it presents in a true bird. In the latter, the
end of the wing answers to the thumb and two fingers of my hand; but the
metacarpal bones, or those which answer to the bones of the fingers
which lie in the palm of the hand, are fused together into one mass; and
the whole apparatus, except the last joints of the thumb, is bound up in
a sheath of integument, while the edge of the hand carries the principal
quill feathers. In the _Archæopteryx_, the upper-arm bone is like that
of a bird; and the two bones of the fore-arm are more or less like those
of a bird, but the fingers are not bound together--they are free. What
their number may have been is uncertain; but several, if not all, of
them were terminated by strong curved claws, not like such as are
sometimes found in birds, but such as reptiles possess; so that, in the
_Archæopteryx_, we have an animal which, to a certain extent, occupies a
midway place between a bird and a reptile. It is a bird so far as its
foot and sundry other parts of its skeleton are concerned; it is
essentially and thoroughly a bird by its feathers; but it is much more
properly a reptile in the fact that the region which represents the hand
has separate bones, with claws resembling those which terminate the
fore-limb of a reptile. Moreover, it had a long reptile-like tail with a
fringe of feathers on each side; while, in all true birds hitherto
known, the tail is relatively short, and the vertebræ which constitute
its skeleton are generally peculiarly modified.

[Illustration: FIG. 5.--ICHTHYORNIS DISPAR (Marsh).

(Side and upper views of half the lower jaw; and side and end views of a
vertebra.)]