FFC showed me this. At the corner of Carlisle Rd and Old Lowell Rd in southern Westford there is a old cemetery. An Indian is said to be buried there.Looking at the gravestones, there are a number of interesting and suggestive headstone shapes. For one thing there are numerous "manitou" shaped stones and also on the right towards the back is a headstone that is distinctly off-center as a manitou stone. It matches the 'boat rudder' shape I have discussed before.
But what is that in the back? Is that a rock pile? Here is a closeup:
Could this be the Indian's grave? It matches well with the type of piles we have guessed were burial piles. It is on the ground and contains a white stone. This is un-looked-for confirmation to those guesses. (See here and here and elsewhere).
[While looking in Technorati for references to mention above, I came across this. Taken together these things strongly suggest that rock piles can be Indian graves. I guess this is not a surprise.]