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
Collins–Valentine line Collins–Valentine line The Collins–Valentine line, or Valentine–Collins line, is the boundary at approximately 45 degrees north latitude that separates the province of Quebec from the states of New York and Vermont. It was surveyed and marked by survey monuments in 1771–3 by John Collins, surveyor-general of Quebec, and Thomas Valentine, a commissioner appointed by the government of New York. Quebec had been a French colony until the conclusion of the Seven Years' War in 1763, when it became a British colony. In the 1760s, the region that would later become a state of Vermont was considered by authorities in Britain