Cancellus spongicola
The Miner Hermit Crab differs from all others by living in a hole bored into a piece of limestone rock, rather than in a snail shell. The two claws are similar in size and shape and, with the first legs, can be pulled in to be an effective protective stopper for the crab inside. At night, the crab walks around pulling its rock behind it... http://portphillipmarinelife.net.au/species/5457