We shall see
this presently. Let us first glance at the advances among the
inhabitants of the seas.
The most important and stimulating event in the seas is the
arrival of the Ammonite. One branch of the early shell-fish, it
will be remembered, retained the head of its naked ancestor, and
lived at the open mouth of its shell, thus giving birth to the
Cephalopods. The first form was a long, straight, tapering shell,
sometimes several feet long. In the course of time new forms with
curved shells appeared, and began to displace the
straight-shelled. Then Cephalopods with close-coiled shells, like
the nautilus, came, and--such a shell being an obvious
advantage-- displaced the curved shells. In the Permian, we saw,
a new and more advanced type of the coiled-shell animal, the
Ammonite, made its appearance, and in the Triassic and Jurassic
it becomes the ogre or tyrant of the invertebrate world.
Sometimes an inch or less in diameter, it often attained a width
of three feet or more across the shell, at the aperture of which
would be a monstrous and voracious mouth.
The Ammonites are not merely interesting as extinct monsters of
the earth's Middle Ages, and stimulating terrors of the deep to
the animals on which they fed.
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