Shell deformity. Possibly a congenital humpback condition of the spinal column known as Kyphosis?
At the boat put in on Mountain Lake (accessed from portage trail from Buzzard Lake). Not much here. I cut the seed heads off about 15-30 stems that went to seed. (And bagged them out with my garbage. There are probably less than 100 plants in a confined area as of Nov 2022.
Firm. Each egg about the size of a chia seed.