But the Jurassic is particularly memorable because its strata have
yielded two fine specimens of the first known bird, _Archæopteryx_.
These were entombed in the deposits which formed the fine-grained
lithographic stones of Bavaria, and practically every bone in the body
is preserved except the breast-bone. Even the feathers have left their
marks with distinctness. This oldest known bird--too far advanced to be
the first bird--was about the size of a crow and was probably of
arboreal habits. Of great interest are its reptilian features, so
pronounced that one cannot evade the evolutionist suggestion. It had
teeth in both jaws, which no modern bird has; it had a long lizard-like
tail, which no modern bird has; it had claws on three fingers, and a
sort of half-made wing. That is to say, it does not show, what all
modern birds show, a fusion of half the wrist-bones with the whole of
the palm-bones, the well-known carpo-metacarpus bone which forms a basis
for the longest pinions. In many reptiles, such as Crocodiles, there are
peculiar bones running across the abdomen beneath the skin, the
so-called "abdominal ribs," and it seems an eloquent detail to find
these represented in _Archæopteryx_, the earliest known bird. No modern
bird shows any trace of them. [Illustration: SKELETON OF AN EXTINCT
FLIGHTLESS TOOTHED BIRD, HESPERORNIS
(_After Marsh._)
The bird was five or six feet high, something like a swimming ostrich,
with a very powerful leg but only a vestige of a wing. There were sharp
teeth in a groove. The modern divers come nearest to this ancient
type.]
[Illustration: SIX STAGES IN THE EVOLUTION OF THE HORSE, SHOWING GRADUAL
INCREASE IN SIZE
(_After Lull and Matthew._)
1. Four-toed horse, Eohippus, about one foot high. Lower Eocene, N.
America.
2. Another four-toed horse, Orohippus, a little over a foot high. Middle
Eocene, N. America.
3. Three-toed horse, Mesohippus, about the size of a sheep. Middle
Oligocene, N. America.
4. Three-toed horse, Merychippus, Miocene, N. America. Only one toe
reaches the ground on each foot, but the remains of two others are
prominent.
5. The first one-toed horse, Pliohippus, about forty inches high at the
shoulder. Pliocene, N. America.