I think this may be a Petrolisthes eriomerus (Flattop Crab), but it either doesn't have or didn't show me its pincers.
Have this as a pet in my dorm.
Pleuroncodes planipes eaten by petrolisthes
Here's the second of two Petrolisthes eriomerus (Flattop Crab) found under rocks during the minus tide. The carapace measured about 1.5".
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.