Wallace Line by the Sahul Shelf to New Guinea. The biogeographic boundary known as Lydekker's Line, which separates the eastern edge of Wallacea from the Australian region, has a similar origin to the Wallace line. During ice age glacial advances, when the , both Asia and Australia were united with what are now islands on their respective continental shelves as continuous land masses, but the deep water between those two large continental shelf areas was, for over 50 million years, a barrier that kept the flora and fauna of Australia separated from those of Asia. Wallacea consists of islands that were not
Purchase line at present-day Cherry Tree, Pennsylvania. This was agreed to as the "nearest point" of the treaty. This became the tri-point between present-day Clearfield, Cambria, and Indiana counties, although the borough of Cherry Tree, Pennsylvania was later included entirely in Indiana for convenience. The line is still a boundary through most of its length: in Armstrong County running ESE from Kittanning it separates the townships of Rayburn and Valley (north) from Manor and Kittanning (south). There is gap through the town of Cowanshannock, but at the knick point of the boundary between Armstrong County and Indiana County the line begins again,