These remains are often in the most exquisite state of preservation.
The valves of the shell-fishes are commonly adherent; the long spines
of some of the sea-urchins, which would be detached by the smallest
jar, often remain in their places. In a word, it is certain that these
animals have lived and died when the place which they now occupy was
the surface of as much of the chalk as had then been deposited; and that
each has been covered up by the layer of Globigerina mud, upon which the
creatures imbedded a little higher up have, in like manner, lived and
died. But some of these remains prove the existence of reptiles of vast
size in the chalk sea. These lived their time, and had their ancestors
and descendants, which assuredly implies time, reptiles being of slow
growth.
There is more curious evidence, again, that the process of covering up,
or, in other words, the deposit of Globigerina skeletons, did not go on
very fast. It is demonstrable that an animal of the cretaceous sea might
die, that its skeleton might lie uncovered upon the sea-bottom long
enough to lose all its outward coverings and appendages by putrefaction;
and that, after this had happened, another animal might attach itself
to the dead and naked skeleton, might grow to maturity, and might itself
die before the calcareous mud had buried the whole.
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