Coral fossils from Lake Huron

Approx. 350 Mill. years old from the Devonian period: Corals in Lake Huron. This era was named after Devon, UK, where fossils of this type were first discovered. The Devonian period lasted 60 Mill. years, from 419 Mill to 358 Mill years ago.

State of Michigan Internet entry:
Devonian fossils of Michigan are marine, consisting of brachiopods, crinoids, corals, bryzoans, trilobites, gastropods, fish, blastoids, and cephalopods. Carboniferous fossils are usually found in central Michigan, and are not usually well preserved.