2. Vestālis virginis: the Vestals were a kind of nuns, six in number, who were priestesses of Vesta. It was their duty to keep the fire on the altar in her temple in the Forum burning constantly. “Her altar, with its ever-burning fire, was the family hearth of the state, from which the household fires were kindled at certain dates.” Lanciani, Anc. Rome, Ch. VI.
fīlius: in apposition with quī, subject of putātus est.
quantum putātus est: ‘as he was thought’ ＝ ‘as it was thought’; note that the Latin prefers the personal construction where we prefer the impersonal.
3. is: emphatic position.
cum … latrōcinārētur: the student should note the different uses of cum, viz.: Temporal, with Indicative or Subjunctive; Causal and Concessive, with Subjunctive alone; cf. cum … compāruisset, Ch. 2; cum … habērent, Ch. 2; cum … ēgissent, Ch. 18.
4. decem et octō annōs nātus (nāscor): ‘having been born eighteen years’ ＝ ‘eighteen years old.’ The more common expression for the numeral is duodēvīgintī. Cf. annōrum trium et vīgintī, Bk. II, Ch. 6; annum agēns vīcēsimum aetātis, Bk. III, Ch. 7.
5. urbem exiguam: remains of this city are still found on the Palatine Hill.
Palātīnō monte: the Palatine Hill, one of the seven hills of Rome. The others were the Capitoline, Quirinal, Aventine, Esquiline, Viminal, and Caelian.
XI Kal. Māiās: the full expression would be ante diem ūndecimum Kalendās Māiās, April 21. “In the Roman calendar it coincided with the Palilia, or feast of Pales, the guardian divinity of shepherds.”
6. Olympiadis: the Greeks reckoned time by periods of four years, called Olympiads from the Olympian Games, which were celebrated at that interval. The starting point was 776 B.C. Hence the third year of the sixth Olympiad would be 753 B.C. Some prefer to recognize 754 as the date of the founding of the city.