How to indentify porcelain crab

[Wolf89]

I live on the ocean, and I know there are porcelain crabs out there, but there are also a lot of those bad crab species. How can I tell the difference for sure?

 

[Wolf89]

Found it on google - "Porcelain crabs can be distinguished from true crabs by the apparent number of walking legs (three instead of four pairs; the fourth pair is reduced and held against the carapace), and the long antennae originating on the front outside of the eyestalks. "