Bob,
That seems to be what they are, earthworks, but it sounds like many of them are still in play:
A landscape feature unique to Hoylake is the presence of a number of ‘cops’ within the site around which the golf course has (throughout its evolution) played over, around or alongside. The ‘cops’ marked and delineated the old field boundary lines and can be best described as raised, turf-covered dykes (walls) forming low, linear ridges. Over time such has been their significance to the site that they have been incorporated into many of the holes, informing both hole design and strategy.