The latter groups soon became
extinct, but the former continued for some millions of years, and
became remarkably adapted to marine life, like the whale at a
later period.
The Ichthyosaur of the Jurassic is a remarkably fish-like animal.
Its long tapering frame--sometimes forty feet in length, but
generally less than half that length--ends in a dip of the
vertebral column and an expansion of the flesh into a strong
tail-fin. The terminal bones of the limbs depart more and more
from the quadruped type, until at last they are merely rows of
circular bony plates embedded in the broad paddle into which the
limb has been converted. The head is drawn out, sometimes to a
length of five feet, and the long narrow jaws are set with two
formidable rows of teeth; one specimen has about two hundred
teeth. In some genera the teeth degenerate in the course of time,
but this merely indicates a change of diet. One fossilised
Ichthyosaur of the weaker-toothed variety has been found with the
remains of two hundred Belemnites in its stomach. It is a flash
of light on the fierce struggle and carnage which some recent
writers have vainly striven to attenuate.
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