Jim,
The crab you have is an anenome crab. True porcelain crabs have darker colors with fine stripes, and larger claws. Porcelain crabs usually stay on the undersides of rocks and filter feed. My wholesaler often mislables them, I knew I had a good chance of getting you the right crab.

True porcelain crab
porcelaincrab - hosting porcelain crab

Anenome crab
anenomecrab - hosting porcelain crab