RCAHMS says there's this, which sounds similar:

"NB23SW 21 224 327. On the W edge of the ridge, at a distance of 57m NNW of the ring of standing stones of Cnoc Fillibhir Bheag (NB23SW 2) there is a sub-circular annular setting of low stones and many buried stones exposed in abandoned peat cuttings, varying between 3.4m and 4.8m internal diameter, from which the ring can be seen on the horizon. "

So in determining what it is, that doesn't help much...