teenth and the beginning of the nineteenth centuries,
Lamarck and Cuvier, lived in the Paris basin, a vast cemetery of corals,
shells, and mammals; and not far from extensive deposits of cretaceous
rocks packed with fossil invertebrates. With their then unrivalled
knowledge of recent or existing forms, they could restore the
assemblages of extinct animals which peopled the cretaceous ocean, and
more especially the tertiary seas and lakes.

Lamarck drew his supplies of tertiary shells from the tertiary beds
situated within a radius of from twenty-five to thirty miles from the
centre of Paris, and chiefly from the village of Grignon, about ten
miles west of Paris, beyond Versailles, and still a rich collecting
ground for the students of the Museum and Sorbonne. He acknowledges the
aid received from Defrance,[81] who had already collected at Grignon
five hundred species of fossil shells, three-fourths of which, he says,
had not then been described.

Lamarck's first essay ("_Sur les fossiles_") on fossils in general was
published at the end of his _Systeme des Animaux sans Vertebres_
(pp. 401-411), in 1801, a year before the publication of the
_Hydrogeologie_. "I give the name _fossils_," he says, "to remains of
living beings, changed by their long sojourn in the earth or under
water, but whose forms and structure are still recognizable.

"From this point of view, the bones of vertebrate animals and the
remains of testaceous molluscs, of certain crustacea, of many
echinoderms, coral polyps, when after having been for a long time
buried in the earth or hidden under the sea, will have undergone an
alteration which, while changing their substance, has nevertheless
destroyed neither their forms, their figures, nor the special
features of their structures."

He goes on to say that the animal parts having been destroyed, the shell
remains, being composed of calcareous matter. This shell, then, has lost
its lustre, its colors, and often even its nacre, if it had any; and in
this altered condition it is usually entirely white. In some cases where
the shells have remained for a long period buried in a mud of some
particular color, the shell receives the same color.

"In France, the fossil shells of Courtagnon near Reims, Grignon near
Versailles, of what was formerly Touraine, etc., are almost all
still in this calcareous state, having more or less completely lost
their animal parts--namely, their lustre, t