Are these two different types of worm?

[Cgs928]

Are these worms different from one another? Is anyone able to name them? And what does their appearance mean from an ecological standpoint?

[indominus rex]

I believe they are Calcareous Tube worm that normally grows on rocks reefs and other creatures in the ocean. Like this one that grew on my Belemnite form Holzmaden. And here is a Image from a modern day one. Also could you give me any information on the location?

[Tidgy's Dad]

They both look like Serpula to me, or at least a serpulid worm. 

They are epibionts which means they grow on top of another organism, in this case probably bivalve shells. 

[Ludwigia]

Yes. Serpula is correct.

[Pagurus]

1 hour ago, Cgs928 said:

what does their appearance mean from an ecological standpoint?

 

I agree they are serpulid worms. Try googling serpulid and reef-building, or reef-building tube-worm. Very often there are just a few tube worms attached to a mollusk, to rocks, and to seaweed, but in some locations they grow on top of the tubes of their predecessors, forming reefs that  provide important habitat to other ocean animals. Including hermit crabs. 

[Calvert Cliff Dweller]

We have similar worms in the Maryland Miocene Calvert formation.