Glenna, I'm not sure about the history of this type of grave (raised in a mound), but I've seen many like that in Savannah. On the coast, they used a material called "tabby" which has sea shells in it. These were usually crushed/broken sea shells added to the tabby mixture. Besides shells, I believe tabby was made from sand, but I don't know what the other ingredients were. I've never seen tabby with large shells imbedded in it. Darleen Miller