A rock crab is a large landbound crustacean whose body is almost entirely composed of hard minerals, giving it its formidable protection. The outer shell and outer limb carapace of its body, when compressed together, gives the crab the shape of an oblate spheroid rock. When provoked however, it relinquishes its natural disguise and shows its crab-like shape. The rock crab's body is about 3 feet from end to end, and its arms and jagged, barbed scissors when unfolded reach about two feet away. Rock crabs weigh between 165 and 310 pounds.