While taking pictures, I was sort of paying attention to the historian giving the tour but I should have taken notes. I know he mentioned a Fuller and Soule who did the gravestone carvings in the 1700s. It was mentioned how at first the mouth was a bit grim on the carved head but then it moved toward a mouth that had a bit of a smirk and even a heart.
The third and fourth photo shows how the gravestone carvings started using a willow tree with the last photo really showing off the skills and detail of the carvings.
I did find one posting on the Plympton Cemetery that talks about the headstones and Soule family.