I have already elsewhere said what should be thought of this so-called universal overturning of the globe; I return to fossils.
"It is very true that, of the great quantity of fossil shells gathered in the different countries of the earth, there are yet but a very small number of species whose living or marine analogues are known.

Nevertheless, although this number may be very small, which no one will deny, it is enough to suppress the universality announced in the proposition cited above.
"It is well to remark that among the fossil shells whose marine or living analogues are not known, there are many which have a form closely allied to shells of the same genera known to be now living in the sea.

However, they differ more or less, and cannot be rigorously regarded as the same species as those known to be living, since they do not perfectly resemble them.

These are, it is said, extinct species.
"I am convinced that it is possible never to find, among fresh or marine shells, any shells perfectly similar to the fossil shells of which I have just spoken.

I believe I know the reason; I proceed to succinctly indicate, and I hope that it will then be seen, that although many fossil shells are different from all the marine shells known, this does not prove that the species of these shells are extinct, but only that these species have changed as the result of time, and that actually they have different forms from those individuals whose fossil remains we have found." Then he goes on in the same strain as in the opening discourse, saying that nothing terrestrial remains constant, that geological changes are continually occurring, and that these changes produce in living organisms a diversity of habits, a different mode of life, and as the result modifications or developments in their organs and in the shape of their parts.
"We should still realize that all the modifications which the organism undergoes in its structure and form as the result of the influence of circumstances which would influence this being, are propagated by generation, and that after a long series of ages not only will it be able to form new species, new genera, and even new orders, but also each species will even necessarily vary in its organization and in its forms.
"We should not be more surprised then if, among the numerous fossils which occur in all the dry parts of the globe and which offer us the remains of so many animals which have formerly existed, there should be found so few of which we know the living analogues.