From past files .
This crab lives commensally with sea anemones, and is a filter feeder.
When I find a porcelain crab, I always check the thumb joint and mouthpieces to see if they are blue or red. These are blue, so it's a Petrolisthes eriomerus (Flattop Crab).
The little mud crab
This is a beautiful Petrolisthes eriomerus (Flattop Crab) with a 1" carapace, a porcelain crab identified with its blue joints. It was under a rock during a minus tide.
Crustacean that lives in the low intertidal zone , is under the rocks. Chelae has a pair of three pairs of walking legs and a pair of modified legs.
These small porcelain crabs were quite common under rocks in the mid-intertidal.
Porcelain crabs are decapod crustaceans in the widespread family Porcellanidae, which superficially resemble true crabs. They are typically less than 15 mm (0.6 in) wide, and have flattened bodies as an adaptation for living in rock crevices. They are delicate, readily losing limbs when attacked, and use their large claws for maintaining territories.