2. A eunuch attached to the Egyptian court, and tutor of Arsinoe, youngest daughter of Ptolemy Auletes. [ARSINOE, No. 6.] Towards the end of B. C. 48 Ganymedes accompanied Arsinoe in her flight from Alexandria to the Aegyptian camp; and, after assassinating their leader, Achillas [ACHILLAS], he succeeded to the command of the troops, whose favour he had secured by a liberal donative. Ganymedes, by his skilful dispositions and unremitting attacks, greatly distressed and endangered Caesar, whom he kept besieged in the upper city of Alexandria. By hydraulic wheels, he poured sea-water into the tanks and reservoirs of the Roman quarter; cut off Caesar's communication with his fleet, equipped two flotillas from the docks, the guardships, and the trading vessels, and twice encountered Caesar, once in the roadstead, and once in the inner harbour of Alexandria. But after her brother Ptolemy joined the insurgents, the power of Arsinoe declined, and Ganymedes disappears from history. (Hirt. Bell. Alex. 4-24; D. C. 42.39_44; Lucan, 10.520_531.)