This Petrolisthes eriomerus (Flattop Crab) has a darker carapace than another I found of the same size, 1". The detail is beautiful!
This 1" Petrolisthes eriomerus (Flattop Crab) was paler than another I found. There were dozens of tiny ones.
Here's a blue Petrolisthes eriomerus (Flattop Crab), with a carapace
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.