This is a piece of Tyndall limestone witch contains a fossilized specimen of an ancient sea bottom dwelling organism called Recptaculites.
Thought to be closely related to modern day sponges these organisms were fairly abundant during the Ordovican era going back as far as 500 million years ago.
Here's your chance to own one of Earth's first living organisms from 250 million years before the dinosaurs.
When you call please mention you found this ad listing on OKz.ca