👉 Tridontium is a type of fossilized sea snail, which has been found in various environments and was most commonly associated with the Burgess Shale in England. The name "tridontium" comes from the combination of "tridon" (a term for sea snails) and "tumulus," meaning the formation of a rock mass at the bottom of an ocean, which is often associated with the Burgess Shale.