Under rock in shallow rockpool - 20+ of them.....
No interactions present.
Porcelain crab does not seem a very apt name for this crab with massive unequal claws with long fringes of hairs on claws and legs. The nearly circular carapace is a feature of these crabs; our other species of porcelain crab is Pisidia longicornis; it has narrow claws and no hairs on the claws. Both have very long antennae.
Porcelaneous (Zool.) Having a smooth, compact shell without pores
I have quite a few pictures of these in assorted clothing. But it is the underside which shows off the porcelaneous nature - see Ruraidh's here - http://www.ispot.org.uk/node/357440
Lat/Lng: 49.1, -2.1
OS grid ref: S^9518