Between the islands of the Malay archipelago from Sumatra to New Guinea, and the neighbouring Asiatic continent, no definite relations appear ever to have existed, and no distinctly marked boundary for Asia has been established by the old geographers in this quarter.
It is usually regarded as the Chretes or Chremetes of Hanno, and the Nachyris and Bambotus of the Greeks and Romans, but it is not possible definitely to identify it with any of the rivers on Ptolemy's map. Idrisi and other medieval Arabian geographers undoubtedly refer to it.
At that period geographers regarded the Senegal as the termination of the Niger, a theory held until Mungo Park's demonstration of the eastward course of that stream.
1200, however, the Arabian geographers mention a tributary, the Tharthar, navigable in flood time, which flowed from the Jaghigagh branch of the Khabur, a tributary of the Euphrates, to the Tigris.
The interior of the continent west of 135° and north of the Musgrave ranges is usually termed by geographers the Australian Steppes.