(Ἀρσινόη).
1. The mother of Ptolemy I., king of Egypt, was originally a concubine of Philip, the father of Alexander the Great, and was given by Philip to Lagus, a Macedonian, while she was pregnant with Ptolemy. Hence Ptolemy was regarded by the Macedonians as the son of Philip. (Paus. 1.6.2; Curt. 9.8; Suidas, s. v. Λάγος.)