From: 'St. Peter's Basilica - A Virtual Tour'
Also to be admired is the very elegant crafting of the capitals crowning
the columns at the sides of the altars, in fluted porphyry, yellow and
ancient yellow granite. The last of these flank the central altarpiece
while two identical ones flank the corresponding altar dedicated to St.
Processo and St. Martiniano in the opposite right hand transept.
The decoration of
this central altar was extremely problematic and the final result is far
from satisfactory. In 1822, a mosaic copy of the famous "Crucifixion of
St. Peter" hanging in the Vatican Pinacoteca, a work by Guido Reni in
which Caravaggio's influence on him was strongest, was placed here as
a replacement for an altarpiece by A. Ciampelli showing the above mentioned
saints. This mosaic has, however, recently been moved over the altar on
the left. At the sides of the altar are two round mosaics by V. Camuccini,
representing "St. Simon" and "St. Jude."
From: 'The Mosaics
of Saint Peter's by Frank DiFrederico
Originally on this altar was a painting of 1630 by Agostino Ciampelli
representing saints Simon and Jude. In February 1814 it was replaced by
the mosaic after Guido Reni's Crucifixion of Saint Peter, which previously
had been in the sacristy. The dedication of the altar to saints Simon
and Jude was then memorialized by two mosaic ovals representing the saints
on the walls on the sides of the altar... Crucifixion of Saint Peter was
in turn replaced by Saint Joseph, which had been commissioned by Pope
John XXIII. The painting by Achille Funi was presented to the mosaic
studio in 1961. The mosaic by Virgilio Cassio, Odoardo Anselmi, Silvio
Secchi, Fabrizio Parsi, and Giulio Perificati was placed on the altar