From 25 B.C. the Roman province of Africa comprised the whole of the region between the mouth of the Ampsaga (Wad Rummel, Wad el Kebir) on the west, and the two tumuli called the altars of the Philaeni, the immutable boundary between Tripolitana and Cyrenaica, on the east (Tissot ii.
During the Roman period, according to Pliny, there were settlements of 26 indigenous tribes extending from the Ampsaga as far as Cyrenaica.
Of Numidia (see under Juba), with the river Ampsaga as the eastern frontier (Plin.
It retained its independence till the time of Augustus, who in 25 B.C. bestowed the sovereignty of the previously existing kingdom upon Juba II., king of Numidia, at the same time uniting it with the western portion of Numidia, from the Mulucha to the Ampsaga, which received the name of Mauretania Caesariensis, while the province that had previously constituted the kingdom, or Mauretania proper, came to be known as Mauretania Tingitana (see Mauretania).
It is in this sense that the name Numidia is used by Polybius and all historians down to the close of the Roman republic. The Numidians, as thus defined, were divided into two great tribes, - the lvlassyli on the east, and the Massaesyli on the west - the limit between the two being the river Ampsaga, which enters the sea to the west of the promontory called Tretum, now known as the Seven Capes.
Soon afterwards, in 25 B.C., Juba was transferred to the throne of Mauretania, including the whole western portion of the ancient Numidian monarchy as far as the river Ampsaga, while the eastern part was added to the province of Africa, i.e.