Definition: Repeated, thickened, raised structures on the shell or carapace surface, less than the thickness of the shell/carapace and covering a small area of it. Thickenings can be either radial, comarginal, axial or spiral.
Definition: position of an organism in a food web. May be described verbally with descriptors including primary producer, herbivore or carnivore. If described numerically, 1 indicates a primary producer, 2 a herbivore, and so on up the food web.