MARCOU, JULES (1824-1898), Swiss-American geologist, was born at Salins, in the department of Jura, in France, on the 20th of April 1824. He was educated at Besançon and at the college of St Louis, Paris. He worked in early years with J. Thurmann (1804-1855) on the geology of the Jura mountains. In 1847 he went to North America as travelling geologist for the _Jardin des Plantes_, and in the following year in Boston he joined Agassiz, whom he had met in Switzerland, and accompanied him to the Lake Superior region. Marcou spent two years in studying the geology of various parts of the United States and Canada, and returned to Europe for a short time in 1850. In 1853 he published a _Geological Map of the United States, and the British Provinces of North America_. In 1855 he became professor of geology and palaeontology at the polytechnic school of Zurich, but relinquished this office in 1859, and in 1861 again returned to the United States, when he assisted Agassiz in founding the Museum of Comparative Zoology. In 1861 he published his _Geological Map of the World_ (2nd ed. 1875). Of his published papers the more noteworthy are those on the Jura-Cretaceous formations of the Jura, on the "Dyas" (Permian) of Nebraska, and on the Taconic rocks of Vermont and Canada. His other works include _Lettres sur les roches du Jura et leur distribution géographique dans les deux hémisphères_ (1857-1860) and _Geology of North America_ (1858). Marcou died at Cambridge, Mass., on the 17th of April 1898.