Small burrow from Pyrenees (Spain).

[Seracc]

I found it in an area where traces of worms and crustaceans abound, but there are no other remains (shells or corals).

 

I asked on national forum (Spain) and they tell me that it is too big to be a polychaete. They suggested a burrow. 

 

Any other ideas or votes for burrow? 

 

Thanks, 

 

The coin has a diameter of 1.62cm