The clergy's continuing presence in cathedral space even after death was assured in the Middle Ages by the cycles of prayers for the dead. For us that presence becomes most palpable in the surviving tombs which represent a tiny fraction of the monuments that had accumulated over the centuries.
The eighteenth century brought whole scale destruction. Most of the surviving tombs represent bishops, but you can also find one dean, several canons and a few layfolk. During the main construction period of the cathedral bishops were recruited from local noble families and elected by the chapter; many of them had served as canon or dignitary of the chapter.
Note that the first two, Evrard de Fouilloy and Geoffroy d'Eu were buried in the western bays at the center of the nave: the choir had not yet been built. Their inscriptions credit Evrard with the foundations of the cathedral and Geoffroy with the upper parts [of the nave]. After this, bishops were generally buried in the choir. The first bishop who was not a local boy, Guillaume de Mâcon, founded the first chapel to the south side of the nave where he was buried (the tomb no longer survives). In the later Middle Ages bishops were often chosen by the king or Pope. The recumbent tomb effigies (gisants) allow us to see the attributes that distinguished bishops from ordinary clergy: above all, the episcopal miter (pointed headgear) and staff. The outer cape is a chasuble and the inner tunic is a dalmatic: Bishop Evrard's dalmatic is embroidered with frontal birds. You can also see the ends of Evrard's stole appearing below the chasuble and his collar-piece or amict. The bishop's effigy reflects the image of Christ on the trumeau of the central portal.