Encyclopaedia Britannica, 11th Edition, "Armour Plates" to "Arundel, Earls of"

married Lysimachus, king of Thrace, who made over to her the territories of his divorced wife, Amastris. To secure the succession for her own children she brought about the murder of her stepson Agathocles. Lysandra, the wife of Agathocles, took refuge with Seleucus, king of Syria, who made war upon Lysimachus and defeated him (281). After her husband's death Arsinoe fled to Ephesus and afterwards to Cassandreia in Macedonia. Seleucus, who had seized Lysimachus's kingdom, was murdered in 281 by Ptolemy Ceraunus (half-brother of Arsinoe), who thus became master of Thrace and Macedonia. To obtain possession of Cassandreia, he offered his hand in marriage to Arsinoe, and being admitted into the town, killed her two younger sons and banished her to Samothrace. Escaping to Egypt, she became the wife of her full brother Ptolemy II., the first instance of the practice (afterwards common) of the Greek kings of Egypt marrying their sisters. She was a woman of a masterful character and won great influence. Her husband, though she bore him no children, was devoted to her and paid her all possible honour after her death in 271. He gave her name to a number of cities, and also to a district (nome) of Egypt.[1] It is related that he ordered the architect Dinochares to build a temple in her honour in Alexandria; in order that her statue, made of iron, might appear to be suspended in the air, the roof was to consist of an arch of loadstones (Pliny, _Hist. Nat._ xxxiv. 42). Coins were also struck, showing her crowned and veiled on the obverse, with a double cornucopia on the reverse. She was worshipped as a goddess under the title of [Greek: Thea Philadelphos], and she and her husband as [Greek: Theoi adelphoi] (Justin xxiv. 2, 3; Pausanias i. 7). See von Prott, _Rhein. Mus._ liii. (1898), pp. 460 f.