My wife calls this a "special crab".
It is purchased in New York City Chinatown and she claims it is flown in from China !
She always eats it before I can find a crab expert to show it to for identification.
She also said that it must be alive when you cook it,
that if you cook it after it dies it tastes bad,
whereas U.S. east-coast blue-crabs can be cooked after they are dead.
I was outside trimming bushes while my wife was cleaning one of these
crabs. I heard her scream and rushed inside; the crab was pinching
one of her fingers and as I approached the crab it pinched harder
causing her to scream again. I had bypass shears in my hand and
put them close to the problem and my wife yelled "Don't cut my finger off !"
I managed to hook the bypass shears into the gap in the crabs claws
and cut his finger off; but I have never forgotten that my wife would
think that I was going to cut her finger off !