During this phase of the terrestrial evolutions, the continents, to
judge from the fossilised wood which we meet with in the rocks which now
represent it, would be covered with a very rich vegetation, nearly
identical, indeed, with that which we have described in the preceding
sub-period; according to Adolphe Brongniart, the “age of angiosperms”
had fairly set in; the Cretaceous flora displays, he considers, a
transitional character from the Secondary to the Tertiary vegetation;
that the line between the gymnosperms, or naked-seeded plants, and the
angiosperms, having their seeds enclosed in seed-vessels, runs between
the Upper and Lower Cretaceous formations. “We can now affirm,” says
Lyell, “that these Aix-la-Chapelle plants, called Credneria, flourished
before the rich reptilian fauna of the secondary rocks had ceased to
exist. The Ichthyosaurus, Pterodactyle, and Mosasaurus were of coeval
date with the oak, the walnut, and the fig.”[80]
[80] Lyell’s “Elements of Geology,” p. 333.
The terrestrial fauna, consisting of some new Reptiles haunting the
banks of rivers, and Birds of the genus Snipe, have certainly only
reached us in small numbers. The remains of the marine fauna are, on the
contrary, sufficiently numerous and well preserved to give us a great
idea of its riches, and to enable us to assign to it a characteristic
facies.
The sea of the Upper Cretaceous period bristled with numerous submarine
reefs, occupying a vast extent of its bed--reefs formed of Rudistes
(Lamarck), and of immense quantities of various kinds of corals which
are everywhere associated with them. The Polyps, in short, attain here
one of the principal epochs of their existence, and present a remarkable
development of forms; the same occurs with the Polyzoa (Bryozoa) and
Amorphozoa; while, on the contrary, the reign of the Cephalopods seems
to end. Beautiful types of these ancient reefs have been revealed to us,
and we discover that they have been formed under the influence of
submarine currents, which accumulated masses of these animals at certain
points. Nothing is more curious than this assemblage of
_Rudistes_--still standing erect, isolated or in groups--as may be seen,
for instance, at the summit of the mountains of the _Cornes_ in the
Corbières, upon the banks of the pond of Berre in Provence, and in the
environs of Martigues, at La Cadière, at Figuières, and particularly
above Beausset, near Toulon.
“It seems,” says Alcide D’Orbigny, “as if the sea had retired in order
to show us, still intact, the submarine fauna of this period, such as it
was when in life. There are here enormous groups of _Hippurites_ in
their places, surrounded by Polyps, Echinoderms, and Molluscs, which
lived in union in these animal colonies, analogous to those which still
exist in the coral-reefs of the Antilles and Oceania. In order that
these groups should have been preserved intact, they must first have
been covered suddenly by sediment, which, being removed by the action of
the atmosphere, reveals to us, in their most secret details, this Nature
of the past.”
In the Jurassic period we have already met with these isles or reefs
formed by the accumulation of Coral and other Zoophytes; they even
constituted, at that period, an entire formation called the _Coral-rag_.
The same phenomenon, reproduced in the Cretaceous seas, gave rise to
similar calcareous formations. We need not repeat what we have said
already on this subject when describing the Jurassic period. The coral
or madrepore isles of the Jurassic epoch and the reefs of Rudistes and
Hippurites of the Cretaceous period have the same origin, and the
_atolls_ of Oceania are reproductions in our own day of precisely
similar phenomena.