Geikie estimates very highly Guettard's labors in palæontology, saying that "his descriptions and excellent drawings entitle him to rank as the first great leader of the palæontological 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 (Illænus) 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 palæontology," 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 zoölogical merit, in which he gave some good plates and descriptions of fossil fish" (Lyell). Gesner's treatise on petrefactions preceded Lamarck's work in this direction, as did Brander's _Fossillia Hantoniensia_, published in 1766, which contained "excellent figures of fossil shells from the more modern (or Eocene) marine strata of Hampshire. In his opinion fossil animals and testacea were, for the most part, of unknown species, and of such as were known the living analogues now belonged to southern latitudes" (Lyell's _Principles_, eighth edition, p. 46). [85] _Annales du Muséum d'Histoire Naturelle_, vi., 1805, pp. 222-228. [86] _Recueil de Planches des Coquilles fossiles des environs de Paris_ (Paris, 1823). There are added two plates of fossil fresh-water shells (twenty-one species of Limnæa, etc.) by Brard, with sixty-two figures. [87] _Cuvier et Geoffroy Saint-Hilaire. Biographies scientifiques_, par Ducrotay de Blainville (Paris, 1890, p. 446). [88] "Mémoire sur des os fossiles découverts auprès de la ville d'Aix en Provence" (Mém. Acad. Sc., Paris, 1760, pp. 209-220).