A Flattop Porcelain Crab

Petrolisthes eriomerus is distinguished from the other porcelain crab in this area, P. cinctipes, by having blue mouth parts. P. cinctipes has red orange mouth parts and doesn’t hide under rocks as P. eriomerus does. These are small crabs, at the widest it’s carapace is 8mm across. I had a hard time stopping it from skittering under cover and to hold still long enough to take its photo. They are called “porcelain crabs” because if a predator seizes the large pincer it breaks off, a process called autotomy.