The Wallace Line or Wallace’s Line is a faunal boundary line drawn in 1859 by the British naturalist Alfred Russel Wallace and named by English biologist Thomas Henry Huxley that separates the biogeographical realms of Asia and Wallacea, a transitional zone between Asia and Australia. West of the line are found organisms related to Asiatic species; to the east, a mixture of species of Asian and Australian origin is present. Wallace noticed this clear division during his travels through the East Indies in the 19th century. (source)

Max Wilhelm Carl Weber as leader of the Siboga Expedition led him to propose Weber’s line, which encloses the region in which the mammalian fauna is exclusively Australasian, as an alternative to Wallace’s Line. As is the case with plant species, faunal surveys revealed that for most vertebrate groups Wallace’s line was not the most significant biogeographic boundary. The Tanimbar Island group, and not the boundary between Bali and Lombok, appears to be the major interface between the Oriental and Australasian regions for mammals and other terrestrial vertebrate groups. (source)