Neptunus in Greek and Roman Biography and Mythology
the chief marine divinity of the Romans. His name is
probably connected with the verb ναίω or nato, and a
contraction of navitunus. As the early Romans were not a
maritime people, and had not much to do with the sea, the
marine divinities are not often mentioned, and we scarcely
know with any certainty what day in the year was set apart
as the festival of Neptunus, though it seems to have been
the 23rd of July (X. Kal. Sext.). His temple stood in the
Campus Martins, not far from the septa; but respecting the
ceremonies of his festival we know nothing, except that the
people formed tents (umbrae) of the branches of trees, in
which they probably rejoiced in feasting and drinking
(Varro, de Ling. Lat. 6.19; Hor. Carm. 3.28; Paul. Diac. p.
377, ed. Müller; Tertull. de Spect. 6; P. Vict. Reg. Urb.
IX.; Dict. of Ant. s. v. Neptunalia). When a Roman commander
sailed out with a fleet, he first offered up a sacrifice to
Neptunus, which was thrown into the sea (Cic. de Nat. Deor.
3.20; Liv. 29.27). In the Roman poets Neptunus is completely
identified with the Greek Poseidon, and accordingly all the
attributes of the latter are transferred by them to the
former. [POSEIDON.] - A Dictionary of Greek and Roman
biography and mythology, William Smith, Ed.