Hitchhiker ID

[valley]

Hello, anyone know what these are? They came out of my live ocean rock. The crab looks pretty cool and if it’s any good then I hope it doesn’t die during the curing.

 

[ISpeakForTheSeas]

Any chance you could get pics of the other side of this critter?

The crab is a sponge crab (taxonomic family Dromiidae) - not reef safe, but very neat to find; it could be a great sump monster!