4. The wife of Magas, king of Cyrene. In order to put an end to his disputes with his brother Ptolemy II. Philadelphus, Magas had betrothed his only daughter, Berenice, to the son of Ptolemy, but died before the marriage took place. As Arsinoe disapproved of this connexion, she invited Demetrius the Fair, the son of Demetrius Poliorcetes, to Cyrene, in order to become the king of the place and the husband of Berenice. But his beauty captivated Arsinoe; and her daughter indignant at the treatment she had received, excited a conspiracy against him, and caused him to be killed in the arms of her mother. Berenice then married the son of Ptolemy. (Justin, 26.3.) It is not stated of what family this Arsinoe was. Niebuhr (Kleine Seriften, p. 230) conjectures that she was the same as the daughter of Lysimachus [No. 3], who after her banishment to Coptos went to Cyrene, and married Magas.
A Dictionary of Greek and Roman biography and mythology
Smith, William
A Dictionary of Greek and Roman biography and mythology. William Smith, LLD, ed. 1890