Definition of Wallace's line in US English:

Wallace's line

proper noun

  • A hypothetical line, proposed by Alfred Russel Wallace, marking the boundary between the Oriental and Australian zoogeographical regions. Wallace's line is now placed along the continental shelf of Southeast Asia, east of the islands of Borneo, Bali, and the Philippines. To the west of the line Asian animals such as monkeys predominate, while to the east of it the fauna is dominated by marsupials.