Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
Respecting the world of spirits little can be said. The departed
souls of mortal men, the "good" (-manes-) continued to exist as
shades haunting the spot where the body reposed (-dii inferi-), and
received meat and drink from the survivors. But they dwelt in the
depths beneath, and there was no bridge that led from the lower
world either to men ruling on earth or upward to the gods above.
The hero-worship of the Greeks was wholly foreign to the Romans,
and the late origin and poor invention of the legend as to the
foundation of Rome are shown by the thoroughly unRoman transformation
of king Romulus into the god Quirinus. Numa, the oldest and most
venerable name in Roman tradition, never received the honours of
a god in Rome as Theseus did in Athens.