Geoffroy wrote: _Catalogue des mammiferes du Museum National d'Histoire Naturelle_ (1813), not quite completed; _Philosophie anatomique_--t. i., _Des organes respiratoires_ (1818), and t. ii., _Des monstruosites humaines_ (1822); _Systeme dentaire des mammiferes et des oiseaux_ (1st pt., 1824); _Sur le principe de l'unite de composition organique_ (1828); _Cours de l'histoire naturelle des mammiferes_ (1829); _Principes de philosophie zoologique_ (1830); _Etudes progressives d'un naturaliste_ (1835); _Fragments biographiques_ (1832); _Notions synthetiques, historiques et physiologiques de philosophie naturelle_ (1838), and other works; also part of the _Description de l'Egypte par la commission des sciences_ (1821-1830); and, with Frederic Cuvier (1773-1838), a younger brother of G. Cuvier, _Histoire naturelle des mammiferes_ (4 vols., 1820-1842); besides numerous papers on such subjects as the anatomy of marsupials, ruminants and electrical fishes, the vertebrate theory of the skull, the opercula of fishes, teratology, palaeontology and the influence of surrounding conditions in modifying animal forms. See _Vie, travaux, et doctrine scientifique d'Etienne Geoffroy Saint-Hilaire, par son fils M. Isidore Geoffroy Saint-Hilaire_ (Paris and Strasburg, 1847), to which is appended a list of Geoffroy's works; and Joly, in _Biog. universelle_, t. xvi. (1856). GEOFFROY SAINT-HILAIRE, ISIDORE (1805-1861), French zoologist, son of the preceding, was born at Paris on the 16th of December 1805. In his earlier years he showed an aptitude for mathematics, but eventually he devoted himself to the study of natural history and of medicine, and in 1824 he was appointed assistant naturalist to his father. On the occasion of his taking the degree of doctor of medicine in September 1829, he read a thesis entitled _Propositions sur la monstruosite, consideree chez l'homme et les animaux_; and in 1832-1837 was published his great teratological work, _Histoire generale et particuliere des anomalies de l'organisation chez l'homme et les animaux_, 3 vols. 8vo. with 20 plates. In 1829 he delivered for his father the second part of a course of lectures on ornithology, and during the three following years he taught zoology at the Athenee, and teratology at the Ecole pratique. He was elected a member of the academy of sciences at Paris in 1833, was in 1837 appointed to act as deputy for his father at the faculty of sciences in Paris, and in the following year was sent to Bordeaux to organize a similar faculty there. He became successively inspector of the academy of Paris (1840), professor of the museum on the retirement of his father (1841), inspector-general of the university (1844), a member of the royal council for public instruction (1845), and on the death of H.M.D. de Blainville, professor of zoology at the faculty of sciences (1850). In 1854 he founded the Acclimatization Society of Paris, of which he was president.