Ancus Marcius (c.677 BC – 617 BC ; reigned 642 BC – 617 BC) was the legendary fourth king of Rome. He was the son of Marcius (whose father, also named Marcius, had been a close friend of Numa Pompilius) and Pompilia (daughter of Numa Pompilius). According to Festus, Marcius had the surname of Ancus from his crooked arm. Upon the death of the previous king, Tullus Hostilius, the Roman Senate appointed an interrex, who in turn called a session of the assembly of the people who elected the new king.