A domed sandy crab that folds its claws flat across the front until the whole animal is a smooth box with no gaps - which is where the name comes from, and why a box crab in defense looks like a stone with a seam.
The right claw is a tool. It carries a hooked tooth at the base that works exactly like a can opener: the crab grips a snail shell, hooks the lip, and peels the spiral open turn by turn to reach the animal inside. The left claw holds the shell while the right one works, and the two are visibly different shapes because of it.
It spends the day buried in sand with only the eye slits exposed, and hunts at night for snails, hermit crabs and whatever else it can open.
Because both claws are asymmetrical and specialized, a box crab that loses the right one is in trouble until it molts - which is a hazard of building your living around a single tool.
- domed sandy shell with rough ridges, wider than it is long
- claws folded flat against the front, closing the body into a smooth box
- usually buried with only the top of the shell and the eyes showing
- shell up to 8 cm across
