Whenever these radiating chapels are found there is considerable variance both in their number and ground plan. Sometimes there is but one,[458] sometimes two,[459] in the majority of cases three,[460] very seldom four,[461] but frequently five.[462] In plan, the chapels are generally semicircular with or without one or more preceding rectangular bays.[463] Naturally they are vaulted exactly in the manner used for the principal apse of the church or the minor apses of the transept at the time the chapels were built. The usual Romanesque form is the simple half dome like that in Saint Nicolas at Blois, which is especially interesting because it still retains its painted decoration. As the ribbed half dome came in in apse vaulting it appeared in a number of radiating chapels, at Domont and Saint Martin of Étampes, for example, but the usual Gothic form was the chevet vault which corresponds exactly with that over the major apse, except when it is combined with the ambulatory vault in the manner already described,[464] or is of square,[465] circular, polygonal, or irregular plan.[466] In such cases the vaulting is adapted to the plan without any great structural changes from the types found in the remainder of the church. The cathedral of Auxerre (Fig. 84 and Plate III-f), for example, shows the use of a ten-part vault over a square chapel, while Saint Germain also at Auxerre and Saint Remi at Reims (Fig. 87 Plate III-l) have chapels of almost circular plan covered with a vault which is virtually a double Gothic chevet like that of the transept chapels of Soissons and Laon cathedrals already described.[467] BIBLIOGRAPHY This bibliography contains in large measure only titles referred to in the text. For further references see bibliography in Porter, Medieval Architecture. The abbreviations listed in the first column are those used in the notes. Baum Julius Baum Romanesque Architecture in France Baudot and A. de Baudot and A. Perrault-Dabot Perrault-Dabot Archives de la Commission des Monuments Historiques Bond Francis Bond Gothic Architecture in England Borrmann and Richard Borrmann und Joseph Neuwirth Neuwirth Geschichte der Baukunst. 2 vols. Bumpus T. Francis Bumpus A Guide to Gothic Architecture Butler Howard Crosby Butler Abbeys of Scotland Cattaneo Raphael Cattaneo l’Architecture en Italie du VIe au XIe Siècle Caumont Arcis de Caumont Abecedaire ou Rudiment d’Archaeologie Choisy Auguste Choisy Histoire de l’Architecture. 2 vols. Cummings Charles A. Cummings A History of Architecture in Italy. 2 vols. C. M. H. Archives de la Commission des Monuments Historique. 1855-72 Dartein Fernand de Dartein Etude sur l’Architecture Lombarde et sur les origines de l’Architecture Romano-Byzantine. 2 vols. Dehio and von G. Dehio und G. von Bezold Bezold