Thanks for that.
Now here is what is going to probably seem to you like a
really stupid question.....
I have seen sea anemones in rock pools and when the tide is out they are just little blobs on the rocks: it is only when they are covered in water that the tentacles emerge.... so would a bird manage to dislodge one and carry it off while the tentacles were out, or are there species that have exposed tentacles all the time?
Sorry to be such an ignoramus but I'm more into birds (and flowers and fungi) than sea-life. I just thought that someone here might be able to clear up the mystery, knowing how good ID skills are on other parts of this site!