The fourth king of Rome, is said to have reigned twenty-three or twenty-four years, from about b. c. 638 to 614. According to tradition he was the son of Numa's daughter, and sought to tread in the footsteps of his grand­father by reestablishing the religious ceremonies which had fallen into neglect. But a war with the Latins called him from the pursuits of peace. He conquered the Latins, took many Latin towns, transported the inhabitants to Rome, and gave them the Aventine to dwell on. These conquered Latins, according to Niebuhr's views, formed the original Plebs. (Dict. of Ant. s.v. Plebs.) It ia related further of Ancus, that he founded a colony at Ostia, at the mouth of the Tiber ; built a fortress on the Janiculum as a protection against Etruria. and united it with the city by a bridge across the Tiber ; dug the ditch of the Quirites, as it was called, which was a defence for the open ground between the Caelian and the Palatine; and built a prison to restrain offenders, who were increasing (Liv. i. 32, 33 ; Dionys. iii. 36 - 45 ; Cic. de Rep ii. 18 ; Plut. Num. 21 ; Niebuhr, Hist, of Rome, i p. 352, &c.; Arnold, Hist, of Rome, i. p. 19.)