of his writings, however, he
leans to the opinion that species had been lost. Some species, he
observes with great sagacity, "are _peculiar to certain places_, and not
to be found elsewhere." Turtles and such large ammonites as are found in
Portland seem to have been the productions of hotter countries, and he
thought that England once lay under the sea within the torrid zone
(Lyell's _Principles_).

Gesner the botanist, of Zurich, also published in 1758 an excellent
treatise on petrefactions and the changes of the earth which they
testify. He observed that some fossils, "such as ammonites, gryphites,
belemnites, and other shells, are either of unknown species or found
only in the Indian and other distant seas" (Lyell's _Principles_).

Geikie estimates very highly Guettard's labors in palaeontology, saying
that "his descriptions and excellent drawings entitle him to rank as the
first great leader of the palaeontological school of France." He
published many long and elaborate memoirs containing brief descriptions,
but without specific names, and figured some hundreds of fossil shells.
He was the first to recognize trilobites (Illaenus) in the Silurian
slates of Angers, in a memoir published in 1762. Some of his generic
names, says Geikie, "have passed into the languages of modern
palaeontology," and one of the genera of chalk sponges which he
described has been named after him, _Guettardia_. In his memoir "On the
accidents that have befallen fossil shells compared with those which are
found to happen to shells now living in the sea" (Trans. Acad. Roy.
Sciences, 1765, pp. 189, 329, 399) he shows that the beds of fossil
shells on the land present the closest possible analogy to the flow of
the present sea, so that it becomes impossible to doubt that the
accidents, such as broken and worn shells, which have affected the
fossil organisms, arose from precisely the same causes as those of
exactly the same nature that still befall their successors on the
existing ocean bottom. On the other hand, Geikie observes that it must
be acknowledged "that Guettard does not seem to have had any clear ideas
of the sequence of formations and of geological structures."

[84] Scheuchzer's "Complaint and Vindication of the Fishes" (_Piscium
Querelae et Vindiciae_, Germany, 1708), "a work of zooelogical merit, in
which he gave some good plates and descriptions of fossil fish" (Lyell).
Gesner's treatise on petrefactions preceded Lamarck's work