Thirty-five metres to the south of that monument, however, something quieter and considerably more puzzling sits almost unnoticed. An arc of eleven low gneiss stones, none rising more than thirty centimetres from the ground, curves across the hillside in a rough semicircle roughly twelve metres in diameter. Whether this arc once formed the kerb of a passage tomb, where a kerb is a ring of stones defining the outer edge of a cairn, or the perimeter of a stone circle, remains genuinely uncertain. No trace of a cairn survives. To the north of the arc, a single set boulder may be the back stone of a burial chamber that once opened to the southeast, and three further displaced boulders lie to the east of it. The Ordnance Survey six-inch map marked this location simply as "stone circles (site of)", a designation that acknowledged uncertainty even then.

The ambiguity of what survives here is at least partly the result of human interference. According to Stefan Bergh's 1995 study of the Knocknarea complex, this monument is likely one of several on the mountain that were disturbed in the early 1800s by Richard Chamber Walker, a local landowner who was also an antiquarian. The combination of those two roles, landowner and self-taught archaeologist, was not unusual in that period, though the results were often damaging. Walker's interventions across the summit appear to have left several monuments in the fragmentary condition they occupy today. Seán Ó Nualláin, writing in his 1989 survey of the megalithic tombs of County Sligo, considered the arc more consistent with a tomb kerb than a true stone circle, though the absence of any cairn material makes a firm conclusion difficult.

The site is a national monument, number 153, in state care. It sits within an unusually dense concentration of prehistoric monuments on and around the Knocknarea summit, and that density is itself part of what makes this particular fragment worth pausing over. Stripped of its cairn, possibly robbed of its chamber stones, and recorded under the wrong category on nineteenth-century maps, it is a monument that has spent a long time being misread.