The effect is deliberate but slightly improvised: the slabs, each carved separately, have been positioned under an arch in the east wall of the north transept, one lying on its side facing west, forming what amounts to a composite structure rather than a single commissioned piece. It is the kind of thing that rewards a closer look than a casual visitor might give it.

The slab in question measures just over two metres in length and is decorated in a manner typical of seventeenth-century Irish funerary carving. Its central feature is a three-armed cross in relief, with trefoil terminals, a lobed decorative form that appears frequently on monuments of this period. At the centre of the cross sits a lozenge bearing the letters I.H.S., a Christogram derived from the Greek name for Jesus, flanked by a floral motif above and a heart below. Below the cross-head is a three-barred knop, a small raised ornament, and the shaft of the cross rises from a calvary mount carved with a skull and crossbones, a conventional symbol of mortality found across Catholic funerary art of the period. The marginal inscription runs in Latin in Gothic script and is now difficult to read, but the surviving letters correspond closely to a transcription published by Knowles in 1903, which records: "Here lie Thomas O'Meagher and his wife, Eliza Carran, on whose souls, O Lord, have mercy. This monument was erected by their son.... 1642." The name of the son who commissioned it had, even by Knowles's time, been almost entirely worn away.