Hitchhiking snail or worm?

[the_goodz]

Anyone know what this is? Doesnt leave a web like vermetid snails. Not sure if its a type of worm as I have seen no movement with it. The red base on this one is particularly large with the others on my LPS being only about half this size.

 

[the_goodz]

All of which I will say have a red base to start. Some will develop a white top later.