From: 'St. Peter's Basilica - A Virtual Tour' by Our Sunday Visitor
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
This altar at first contained a painting of saints Martial and Valeria by Giacomo Galli, called "Lo Spadarino." In April 1824 it was replaced by the mosaic after Domenichino's Ecstasy of St. Francis, which is now in the Chapel of the Sacrament, and the picture by "Lo Spadarino" was given to the church of St Caterina della Rota in Rome. It is now in the Chapter House of St. Peter's. At the end of the nineteenth century, the altar was rededicated to the saints Martial and Valeria on the insistence of and through the persistence of the then Bishop of Limoges. A mosaic representing saints Marital and Valeria remained on the altar until 1963, when it was replaced by the mosaic after Guido Reni's Crucifixion of Saint Peter.

The mosaic of Crucifixion of Saint Peter was executed by Bartolomeo Tomberli, Domenico Cerasoli, and Lorenzo Roccheggiani, who received payments for their work from 21 August 1779 to 10 April 1784. The piece was placed in the sacristy in May 1784; in 1814 it was moved to the altar of saints Simon and Jude in the center of the left transept. It was displaced from that site to the right altar in 1963 by the mosaic Saint Joseph Patron of the Universal Church. The painting by Guido Reni is in the Vatican Picture Gallery.

St Lawrence Ruiz (left side) b.1600 Manila, Philippines d. 1637 Nagasaki, Japan. One of the martyrs of Japan. They were beatified by John Paul II in 1981 and canonized in October 1987

St Anthony Maria Gianelli (right side of altar) b. 1789 Cerreto, Italy d. 7 June 1846 Canonized 21 October 1951 by Pius XII