Among the features that hold my attention in a Mediterranean Scallop are the strong, sharp-edged ribs, which are sometimes distinctively squarish in cross-section. They remind me of a corrugated roof, or the core of corrugated cardboard. Corrugated arrangements add great strength to structures, without adding too much weight to them. In a bivalve shell, the corrugations not only add strength, but also help keep the valves aligned and tightly closed, preventing a predator from easily sliding one valve past each other to reach the soft parts inside. You can see variations around the “shell corrugation theme” in other bivalves such as cockles, arks, some oysters, and many others.