Yep, tiny filter feeders with a calcium based tube. LOL They can cut the heck out of your arm though so be careful. I've caught them with my forearm while reaching into my fuge.
I have also wondered about those things. I could never get a good enough picture to ask. Thank you for the question and thank you for the answer. Good job dudes (dudettes)
Vermetid snail, I believe... if you're looking for the real name. Whatever the name, I agree with the others... it should be called "hangnail maker snail" in my book.