Mosaic
Church of San Crisogono in Trastevere, Rome

St. James is on the right.  His pilgrim staff is visible behind his right shoulder.  Chrysogonus is depicted as a young military officer.

Despite Cavallini's thoroughly Roman background he uses the Greek letters  MP θV (for meter theou, "Mother of God") in the space just above the Virgin's chair.

More of St. Chrysogonus
More of St. James the Greater
More of the Virgin and Child