The climate of North
America, and of the land which still connected it with Europe,
was correspondingly genial.
* The great authority on Arctic geology, Heer, who makes this
calculation, puts this flora in the Miocene. It is now usually
considered that these warmer plants belong to the earlier part of
the Tertiary era.
This indulgent period (the Oligocene, or later part of the
Eocene), scattering a rich and nutritious vegetation with great
profusion over the land, led to a notable expansion of animal
life. Insects, birds, and mammals spread into vast and varied
groups in every land. Had any of the great Mesozoic reptiles
survived, the warmer age might have enabled them to dispute the
sovereignty of the advancing mammals. But nothing more formidable
than the turtle, the snake, and the crocodile (confined to the
waters) had crossed the threshold of the Tertiary Era, and the
mammals and birds had the full advantage of the new golden age.
The fruits of the new trees, the grasses which now covered the
plains, and the insects which multiplied with the flowers
afforded a magnificent diet. The herbivorous mammals became a
populous world, branching into numerous different types according
to their different environments.
Pages:
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349