Nemertesia antennina

Nemertesia antennina

Observation - Nemertesia antennina - UK and Ireland. Description: I have No idea what these are, I thought the short spiked version might be some sort of 'sea potato' but then I spotted the tall spike ones in a rock pool. Please help to enlighten me?

I have No idea what these are, I thought the short spiked version might be some sort of 'sea potato' but then I spotted the tall spike ones in a rock pool. Please help to enlighten me?