Rather than lying flat over a burial as intended, a fragment of it was repurposed as a jamb, the vertical side-piece of a lancet window on the exterior east wall of the south transept. The stone, carved to mark a death and likely inscribed with some gravity of purpose, ended up as structural fill.

The fragment dates from the 13th or 14th century and is cut from fossiliferous limestone, a stone formed from ancient marine sediments and visibly embedded with the remains of small organisms. On its face is an incised cross head, meaning a cross carved in shallow relief by cutting lines directly into the stone surface, with each arm terminating in a circular roundel. It is a recognisable decorative form from later medieval funerary carving in Ireland, restrained and formal. How it came to be built into the window rather than remaining in its original context is unrecorded. Medieval builders were pragmatic about reusing dressed stone, and a fragment already shaped and smoothed from an earlier slab would have been useful material. Its precise dimensions remain unknown, a consequence of the position it now occupies, which makes close examination impossible.