Possible stone row alongside track on Clogwyn-yr-Eryr. May be line of fence posts!
Coflein has this:
Row of 4 standing stones, 1 recumbent. Two uprights and recumbent at side of main track, other c. 65m SW. OS 1st ed map of 1891shows a boundary line along this alignment, indicative of stones at fence supports.(JONES.RS/CAP/2003).