Bishop Robert’s choir, removed the apse, and extended the building three bays eastwards.  Bishop Ralph’s contribution to the fabric may be distinguished within by the tall vaulting shafts running up from basement to roof, and without by the flying buttresses.  It is a stately example of late Dec. work, verging on exuberance.  The furniture of the choir with the exception of the throne (15th cent.), and a few misereres in the second row of stalls, is modern.  Note fine old glass in E. window.  The lady chapel at the E. is justly considered one of the finest extant examples of the more chaste Dec. style.  Its builder was Bishop Drokensford, 1326.  The structural design is cunningly contrived.  An octagonal chamber is transformed within into a pentagonal apse by the simple device of resting the three western sides on piers, and thus throwing it into one building with the retrochoir, thereby considerably enhancing the general artistic effect.  The glass in the windows is ancient, but is merely a medley of fragments.  Before examining the Chapter House the visitor should dive through the doorway in the N. choir-aisle, and take a look at the so-called crypt.  It is really only the basement of the chapter house, and was used as the cathedral Treasury.  It is an octagonal chamber with a low vault supported on cylindrical columns.  It now contains an assortment of mediaeval odds and ends, from a fine 14th-cent. wooden door to an urn that once contained a human heart.  Note, besides other things, (1) stone lantern, (2) piscina with carved dog and bone.  The chapter house is reached by a flight of stone steps leading out of the N. transept aisle (turn to the R.).  Note, in passing, the corbels with conventual figures.  The Chapter House is an octagonal chamber of spacious dimensions.  The walls are indented with a recessed arcade, and carry a bench table.  The vaulting springs from single shafts, and is supported in the centre by a massive clustered column.  The building is a finely-executed example of geometric Dec., and dates from the episcopate of William de Marchia (1293-1319).  Note (1) the excellent tracery of the windows, and the fragments of old glass; (2) carved heads in arcading of wall, (3) double archway of door.  Before returning to the nave the visitor should make an examination of the Monuments in the transepts and choir aisles.  Their identity will best be discovered from a glance at the plan provided by the verger.  Here mention will only be made of the most notable.  In S. transept, against S. wall (1) William de Marchia (1319), builder of the chapter house; (2) Viscountess Lisle, with coloured canopy (14th cent.).  In Chapel of St Calixtus (1) shrine of Bishop Beckington, unhappily detached from its original position over his tomb; (2) Treasurer Husee (1309); observe panel with representation of the Trinity.  In S. choir aisle (1) incised slab (said to be one of the earliest in England) of Bishop Bytton, junior