mentioned only in documents of the fourth and fifth
centuries (Not. app.; Pol. Silv. 545), but doubtless the same bridge as
that which was known in the Middle Ages as pons Antoninus (Mirab.
9. 11): pons Antonini in arenula (Graphia IO), pons Ianicularis id est
pons ruptus vulgariter nominatus et tremulus et Antoninus
158, Urlichs). This was partially destroyed in 772, hence the name
ruptus, and rebuilt in 1475 in its present shape by Sixtus IV, from whom
comes its modern name, Ponte Sisto. The start of the first arch of the
older bridge may still be seen. If this identification be correct, the
bridge must have been built by an emperor who bore both names,
Marcus Aurelius or Caracalla, and perhaps by the latter rather than the
former, as he could thus bring the buildings of Severus (Hist. Aug. Sev.
19) into closer connection with the campus Martius.
In 1878, in the river immediately below the first arch of the Ponte
Sisto, were found remains of an earlier bridge and also of a memorial
arch which stood at its entrance (BC 1878, 241
; 1881, 11
; cf. NS 1892,
, 234-235; Mitt. 1911, 238-259
). On some of these remains are
fragmentary inscriptions (CIL vi. 31402-31412
; ILS 769) which record
the rebuilding of arch and bridge by Valentinian I in 365-366 A.D.
Some pieces of bronze statues were also found (PT 179, 195, 197). This
proves that the pons Antoninus was restored by Valentinian, and explains
a reference in Ammianus (xxvii. 3. 3). The name, pons Valentinianus,
must have been in use to some extent in later times, together with the
earlier, for in the Mirabilia (II) both names are found, although, by an
error, they are used of different bridges. It is apparent that the impression made on the Romans by the rebuilding of Valentinian was not strong
enough to cause the displacement of the earlier names, pons Antoninus,
pons Aurelius, by the new official designation (Jord. i. I. 417-420;
, 436; Mayerhofer, Gesch.-Topograph. Studien 44-46, 14;
DuP 58). A fragment of a fluviometer was also found (BC 1892, 139-145