Definition: Plications, undulations or other folds on the shell or carapace surface, less than the thickness of the shell/carapace and covering a small area of it, with thickness remaining consistent across folds.
Definition: Repeated, thickened, raised structures on the shell or carapace surface, comparable to or greater than the thickness of the shell/carapace and covering a notable portion of it. Thickenings can be either radial, comarginal, axial or spiral.
