Two mounds are revealed by LiDAR data (not shown on OS mapping editions 1st-3rd). The proximity to the placename 'The Warren' might suggest pillow mounds? Modern aerial photography shows both sites under heavy tree cover.

Sources include
Environment Agency All Wales LiDAR 2012, 2m resolution
NAW Aerial photography 2006-9
OS 1st edtion 25in mapping

Maritime Officer, RCAHMW, August 2013