LEIDY, JOSEPH (1823–1891), American naturalist and palaeontologist, was born in Philadelphia on the 9th of September 1823. He studied mineralogy and botany without an instructor, and graduated in medicine at the university of Pennsylvania in 1844. Continuing his work in anatomy and physiology, he visited Europe in 1848, but both before and after this period of foreign study lectured and taught in American medical colleges. In 1853 he was appointed professor of anatomy in the university of Pennsylvania, paying special attention to comparative anatomy. In 1884 he promoted the establishment in the same institution of the department of biology, of which he became director, and meanwhile taught natural history in Swarthmore College, near Philadelphia. His papers on biology and palaeontology were very numerous, covering both fauna and flora, and ranging from microscopic forms of animal life to the higher vertebrates. He wrote also occasional papers on minerals. He was an active member of the Boston Society of Natural History and of the American Philosophical Society; and was the recipient of various American and foreign degrees and honours. His Cretaceous Reptiles of the United States (1865) and Contributions to the Extinct Vertebrate Fauna of the Western Territories (1873) were the most important of his larger works; the best known and most widely circulated was an Elementary Treatise on Human Anatomy (1860, afterwards revised in new editions). He died in Philadelphia on the 30th of April 1891.
See Memoir and portrait in Amer. Geologist, vol. ix. (Jan. 1892) and Bibliography in vol. viii. (Nov. 1891) and Memoir by H. C. Chapman in Proc. Acad. Nat. Sc. (Philadelphia, 1891), p. 342.