Deshayes, Gerard Paul

(b. Nancy, France, 24 May 1797; d. Boran-sur-Oise, France, 9 June 1875)

paleontology, malacology.

Deshayes was the son of a physics professor at the École Centrale in Nancy. He began studying medicine at the University of Strasbourg but left in 1820 and went to Paris, where in 1821 he became bachelierès-lettres. He then gave up his medical studies and, as an independent scholar, turned to natural history, particularly geology and malacology. Soon after his arrival in Paris he gave private lectures on geology and led field trips. Those who attended included Élie de Beaumont, d’Archiac, Philippe de Verneuil, Constant Prévost, Desnoyers, and Edmond Hébert. His home soon became a center for exchange of scientific ideas as well as social communications. On behalf of the Paris Academy of Sciences, Deshayes was in Algeria from 1840 to 1842 investigating mollusks, especially those of recent origin. Through his own collecting and through items sent by colleagues in many countries, he amassed a great collection of recent and fossil mollusks that was of exceptional importance because of the many original specimens and types it contained. Circumstances forced Deshayes to sell his collection, together with his comprehensive malacological and paleontological library, to the French government in 1868 for 100,000 francs. Both were turned over to the École des Mines in Paris.

In 1869 Deshayes was appointed professor at the Muséum d’Histoire Naturelle in Paris, occupying the chair of conchology once held by Lamarck, whom he highly regarded. This was Deshayes’s first and only public post. Despite his advanced age, poor health, and the Franco-Prussian War, he enlarged the museum’s malacological collection with tireless zeal and youthful energy. Deshayes was one of the founders of the Société Géologique de France and was several times its president.

An old and worsening heart ailment weakened Deshayes from 1873. He spent some time in Provence and then returned to Boran-sur-Oise, to the region containing the fossils he had described at the beginning of his career. He was survived by his wife and daughter.

In 1824, with his own modest financial means, Deshayes began the publication of Description des coquilles fossiles des environs de Paris. This work, interrupted by descriptions of recent and fossil mollusks of the Peloponnesus and India, was completed in 1837. It is among Deshayes’s most important works. Along with the painstaking description and illustration of 1,074 species of mollusks, predominantly from the Eocene of the Paris Basin, including 660 species first described by him, there is a division of the Tertiary into three periods. The basis for this division was the proportion of living species among the total number of Tertiary forms: in the first (oldest) period, 3 percent; in the second (middle), 19 percent; in the third (most recent), 52 percent. Deshayes joined this with the premise that since the beginning of the Tertiary there had been a continuous decrease in temperature. This three-part division of the Tertiary (1831) agreed in methodological principles and main features with the subdivision of the Tertiary into Eocene, Miocene, and Pliocene proposed by Lyell. After Deshayes was brought into contact with Lyell, he provided for the latter’s use statistical tables of Tertiary mollusk species. They were published in Lyell’s Principles of Geology and constitute an essential support for Lyell’s very important Tertiary subdivisions.

In the following years Deshayes published several large monographs, collections of articles, and compendia. These included a description of fossil mollusks from the Crimea (1838); a work on mollusks from the Algerian expedition, in twenty-five installments interrupted by the February Revolution of 1848 and the actions of envious colleagues (1844–1848); a new edition, in collaboration with Henri Milne-Edwards, of Lamarck’s Histoire des animaux sans vertéres (1833–1858); the continuation of a work begun by J.-B. de Férussac, Histoire naturelle généraleet particulière des mollusques (1839–1851); “Mollusca,” in Cuvier’s Règne animal (1836–1849); an incomplete Traité élémentaire de conchyliologie in three volumes (1839–1857); Conchyliologie de l’îlede la Réunion (Océan Indien) (1863); and Description des animaux sans vertèbres découverts dans le bassin de Paris(1860–1866).

In this last work, Deshayes returned once more to the subject of his first researches. The publications of 1860–1866 and 1824–1837 present his most important contributions.

Deshayes mastered the entire body of the systematic-taxonomic conchology of his time and presented it brilliantly. Even today, despite later publications by other authors, his descriptions of the mollusks of the Tertiary of the Paris Basin form an indispensable basis for further study. His exposition of the stratigraphy of the Paris Basin in the introduction to his Description des animaux sans vertèbres (1860) likewise contains valuable data for an understanding of this sedimentary sequence. Also worth reading are his descriptions in this introduction of the delimitation and definition of species, their life spans, and the reasons for their extinction. Finally, his subdivision of the Tertiary, by means of the proportion of living species of mollusks established in Lyell’s Eocene, Miocene, and Pliocene stages, belongs to the classic methods of biostratigraphy.

BIBLIOGRAPHY

I. Original Works. Besides many journal articles, Deshayes wrote the following books: Description des coquilles fossiles des environs de Paris, 3 vols. (Paris, 1824–1837); Traité élémentaire de conchyliologie avec l’applicationde cette science à la géognosie, 3 vols. (Paris, 1839–1857);Exploration scientifique de l’Algérie. Histoire naturelle des mollusques, 25 pts. (Paris, 1844–1848); Histoire naturelle générate et particulière des mollusques (Paris, 1820–1851), with J.-B. de Férussac; and Description des animaux sans vertèbres découverts dans le bassin de Paris, 3 vols. (Paris,1860–1866). Lists of Deshayes’s papers may be found in Royal Society of London, Catalogue of Scientific Papers (1800–1863), II (London, 1868), 251–254; and (1864–1873), VII (London, 1877), 524.

II. Secondary Literature. On Deshayes or his work, see H. Crosse and P. Fischer, “Nécrologie. G. P. Deshayes,”in Journal de conchyliologie, 24 (1876), 123–127; J. Evans,“Obituary Gérard Paul Deshayes,” in Quarterly Journal of the Geological Society of London, Proceedings, 32 (1876),80–82; and K. Lambrecht, W. Quenstedt, and A. Quenstedt,“Palaeontologi. Catalogus bio-bibliographicus,” in Fossilium catalogus, I, Animalia, 72 (The Hague, 1938), 112–113.

Heinz Tobien