er hand, where the line appeared almost as early as it
did in America, this group underwent a great expansion and ramification,
giving rise not only to the Asiatic and African forms, but also to
several extinct series.

Turning now to the Artiodactyla, we find still another group of mammals,
that of the camels and llamas, which has long vanished from North
America, yet took its rise and ran the greater part of its course in
that continent. From the lower Eocene onward the history of this series
is substantially complete, though much remains to be learned concerning
the earlier members of the family. The story is very like that of the
horses, to which in many respects it runs curiously parallel. Beginning
with very small, five-toed animals, we observe in the successive genera
a gradual transformation in all parts of the skeleton, an elongation of
the neck, limbs and feet, a reduction of the digits from five to two,
and eventually the coalescence of the remaining two digits into a
"cannon-bone." The grinding teeth, by equally gradual steps, take on
the ruminant pattern. In the upper Miocene the line divides into the two
branches of the camels and llamas, the former migrating to Eurasia
and the latter to South America, though representatives of both lines
persisted in North America until a very late period. Interesting
side-branches of this line have also been found, one of which ended in
the upper Miocene in animals which had almost the proportions of the
giraffes and must have resembled them in appearance.

The American Tertiary has yielded several other groups of ruminant-like
animals, some of which form beautifully complete evolutionary series,
but space forbids more than this passing mention of them.

It was in Europe that the Artiodactyla had their principal development,
and the upper Eocene, Oligocene and Miocene are crowded with such an
overwhelming number and variety of forms that it is hardly possible to
marshal them in orderly array and determine their mutual relationships.
Yet in this chaotic exuberance of life, certain important facts stand
out clearly, among these none is of greater interest and importance than
the genealogy of the true Ruminants, or Pecora, which may be traced from
the upper Eocene onward. The steps of modification and change are very
similar to those through which the camel phylum passed in North America,
but it is instructive to note that, despite their many resemblances, the
two series