They are the same species. A soft-shell crab is one that has
just discarded its shell. Crabs which have just shed their shell hide
in rocks or bury themselves in sand and mud to escape predators. They
emerge after the new shell hardens, a quick process.
A large, land hermit crab, which lives on tropical Pacific
islands. The crab is so named because it eats coconuts, is even caught
on coconut used as bait. The meat is considered a delicacy in the
Fisherman often break off the large claw and throw the crab
back into the water. If the break is made at the first joint, the crab
is not harmed. The stone crab can and does sever its own claw at the
first joint (by muscular contraction) to escape from danger.