Not exactly sure what the thing above it - but thanks to Lost Property Office for sending it!
The Huffington Post have made a poll out of the top items. They said: "Little explanation is given to how or why these things might have been left on public transportation. The mind boggles. Let us know what you think is the weirdest, any ideas as to why it might have been left there, and things you have left/seen left behind on public transport."
So far the skull is coming out on top as being the weirdest thing. Feel free to disagree!