The altar-pieces in a Roman Catholic church are always either strictly devotional objects, or it may be, historical subjects (such as the Nativity) treated in a devotional sense. They are sometimes in several pieces or compartments. A Diptych is an altar-piece composed of two divisions or leaves which are united by hinges, and close like a book. Portable altar-pieces of a small size are generally in this form; and among the most valuable and curious remains of early religious art are the Greek and Byzantine Diptychs, sometimes painted, sometimes carved in ivory[1]. A Triptych is an altar-piece in three parts; the two outer divisions or wings often closing as shutters over the central compartment. [Footnote 1: Among the "Casts from Ancient Ivory Carvings", published by the Arundel Society, will be found some interesting and illustrative examples, particularly Class III. Diptych _b_, Class VII Diptych _c_ and Triptych _f_, Class IX. Triptych _k_.] On the outside of the shutters or doors the Annunciation was generally painted, as the mystery which opened the gates of salvation; occasionally, also, the portraits of the votaries or donors. Complete examples of devotional representation occur in the complex and elaborate altar-pieces and windows of stained glass, which often comprehend a very significant scheme of theology.[1]. I give here plans of two of these old altar-pieces, which will assist the reader in elucidating the meaning of others. [Footnote 1: Still more important examples occur in the porches and exterior decoration of the old cathedrals, French and English which have escaped mutilation. These will be found explained at length in the Fourth Series of Sacred and Legendary Art.] The first is the altar-piece in the Rinuccini Chapel in the church of the Santa Croco of Florence. It is necessary to premise that the chapel was founded in honour of the Virgin and Mary Magdalene; while the church is dedicated to the Holy Cross, and belongs to the Franciscans. [Illustration: Altar-piece] The compartments are separated by wood-work most richly carved and gilt in the Gothic style, with twisted columns, pinnacles, and scrolls. The subjects are thus distributed.