Conchologists, he says, did not care to collect or study fossil shells, because they had lost their lustre, colors, and beauty, and they were rejected from collections on this account as "dead" and uninteresting. "But," he adds, "since attention has been drawn to the fact that these fossils are extremely valuable _monuments_ for the study of the revolutions which have taken place in different regions of the earth, and of the changes which the beings living there have themselves successively undergone (in my lectures I have always insisted on these considerations), consequently the search for and study of fossils have excited special interest, and are now the objects of the greatest interest to naturalists." Lamarck then combats the views of several naturalists, undoubtedly referring to Cuvier, that the fossils are extinct species, and that the earth has passed through a general catastrophe (_un bouleversement universel_) with the result that a multitude of species of animals and plants were consequently absolutely lost or destroyed, and remarks in the following telling and somewhat derisive language: "A universal catastrophe (_bouleversement_) which necessarily regulates nothing, mixes up and disperses everything, is a very convenient way to solve the problem for those naturalists who wish to explain everything, and who do not take the trouble to observe and investigate the course followed by nature as respects its production and everything which constitutes its domain. 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.