Identification please

[Etienne 97]

I have just buy a waterbox peninsula 25 on a rock that i have keep i have found theese they seems to be dead or i don't know

 

[BristleWormHater]

I have some of those in my tank. I'm pretty sure those are parchment worms. They are pretty interesting and will send out big filter feeding tendrils. Completely harmless though.