This is an L shaped extension of the room, in the W corner of the trench. Because that corner of the room lacks walls, we are cutting down the area around it to the baulk. Here I am calling the upper portion Locus 15, and whether it will join Locus 8 (the central room) when it gets cut down, or whether I will soon be creating a series of new loci, remains to be determined. Addendum: it never joined Locus 8 or the later Loci 17 and 19, which became the in-room loci. Instead, Locus 15 gave way eventually to Locus 16, which encompassed the entire west corner of the trench, not just an L-shaped portion.