SEMO SANCO. — Semo Sancus Dius Fidius, an Italic divinity of the sky of Jupiter, whose name recalls: a) the Semones of the Arval cult; b) the characteristic of sanctioning, that is, guaranteeing oaths; and c) the epithet proper to Jupiter as guardian of oaths; cf. Σάος πίναος and the Fisos Sancios of the Iguvine Tables.
S. S. had a temple in Rome on the eastern slope of the Quirinal Hill, hence called Sanqualis, just as Sanqualis was the name of the local gate of the Servian enclosure. The temple was dedicated in 446 B.C.; its dedication fell on 5 June (Ovid, Fasti, VI, 213). Two of its ritual particularities are known, both well suited to a divinity of the oath: part of its roof was left open, for the immediate sight of the sky; and inside it preserved certain copper disks (orbes aenei), symbols of the solar disk and reminders of the analogous urfeta (= orbita) of the Umbrian ritual. Treaties were kept in the temple. In the garden adjoining the church of S. Silvestro on the Quirinal, inscriptions relating to the god were discovered. The most important one (though of unknown provenance, discovered in 1879) bears the dedication « Semoni Sanco sancto deo Fidio », placed under the care of the « decuria sacerdotum bidentalium » (CIL, VI, 30.994), a priestly college responsible for the discipline of lightning and which therefore had custody of the temple of that god qui foederà fulmine sancti (Virgil, Aen., XII, 200).
The statue (found in the same locality as the base, now in the Vatican Museum, and representing an Apollo of archaic type) is unrelated to the base. Another sanctuary of the god stood on the Tiber Island, known for the erroneous attribution made to it by the Christian apologists (Justin, Apol., I, 26; Tertullian, Apol., 13), who identified it with Simon Magus, misled by the dedicatory inscription.