Hitchhiker ID help pls

[Ethreal]

Spotted this guy on some LR that I moved today, when he snapped his 'mouth' shut.

It has a spikey shell that fits perfectly in shape and colour with the rock he lives on.

Would anyone be able to tell me what he is please?

 

[the_fish_man]

probably a clam is it hard?

 

[Mouth-Brooder-Fanatic]

whatever it is.... strangely beautiful in a scary-awesome-mysterious-hitchhiker way
when u say mouth, do you mean an actual central opening sort of mouth or a gap where it connects to the live rock?

 

[Ethreal]

Shell is hard.

Mouth as in a gap where it fits the rock - sorry I didnt say it very well.