This view gives one a close up look at a Brownwood Lake Spillway, Pennsylvanian Archaeocidaris sea urchin with spines intact. This one has been partially prepared and can be etched further into the matrix. Since spines can become broken or detached, it is not uncommon for the preparator to gather extra spines from broken sea urchins, while collecting these rare fossils, then adding some of the extra spines to the Archaeocidaris to complete the missing or broken spines. If placed for sale, these should be advertised as composites. It is rare to find any sea urchins with the spines intact. It is very rare to find them when they are 300,000,000 years old. A sudden catastrophe occurred, apparently burying these Archaeocidaris sea urchins, without breaking or tearing off their spines. Collecting them is very difficult and preparing them to properly display them takes a good bit of skill. This is the reason that when you find them for sale, you will not find them selling for low prices.