This is a spectacular, large slab with several large Archaeocederis sp. sea urchin fossils, complete with all spines, in their original rock matrix as found. It dates to the Pennsylvanian Era, approximately 300 million years ago. Extremely well-preserved on their original rock are four (with a partial fifth) large sea urchins and all their associated spines. The color of the fossil urchins is a natural creamy gold color which contrasts with the greenish gray host rock. The rock is fragile and has been reinforced on the back side. All spines are located in their original natural positions and have not been arranged and glued to make an artificially aesthetic fossil as many of these we have seen. The proof in this is the numerous spines that are still partially covered by the host rock surrounding them (rather than all the spines laying ON TOP of the surface of the rock).