Anthracomedusa turnbulli 



Jellyfish 



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by Eugene S. Richardson, Jr. 

 Curator, Fossil Invertebrates 



The strip mines of Illinois are one of the two or three 

 finest areas in the world for collecting invertebrate fossils. 

 Behind the enormous coal mining machines of the Pea- 

 body Coal Company come the geologists, amateur and 

 professional, searching for animals dead a quarter of a 

 billion years. In this article. Dr. Richardson tells of two 

 important finds from Pit Eleven, near Wilmington, Illinois. 

 In two photo reports that follow, the Bulletin presents the 

 lively Museum field crew that worked the area during the 

 past summer, and a survey of the Pit Eleven fauna. 



It's five million, six hundred thousand years to the mile. 

 By the time you've driven fifty miles southwest from the 

 modern center of Chicago, you step out of your car onto the 

 280,000,000-year-old rocks of the Pennsylvanian period in 

 the spoil heaps of a strip mine outside of Wilmington, Illinois. 



You have brought some peanut butter sandwiches (or 

 other delicacy) and a jug of water, of course — and you're 

 going to catch jellyfish. This is a field trip. Perhaps you 

 are one of the Museum's field crew. Or perhaps you're one 

 of the hundreds of amateur collectors who are drawn to this 

 spot. In either case, you have come for fossils, the remains 

 of prehistoric life. More importantly, you are helping in a 

 nearly unique cooperative venture in which Museum scien- 

 tists and amateur collectors pool their efforts to elucidate a 

 part of the story of life in the vanished past. 



Working alone or as members of the Earth Science Club 

 of Northern Illinois, the Des Plaines Valley Geological So- 

 ciety or other such organization, a host of collectors pursue 

 their hobby and the advancement of science at the same 

 time. Returning home tired and happy after a day in the 

 field, these enthusiastic cooperators wash their specimens, 

 carefully identify them, catalog them, and put them ten- 

 derly away in museum-style cabinets. Many an architect 

 in this area would be startled, revisiting what he had thought 

 was to be a recreation room or a utilitarian basement, to 

 find it brightly lighted, lined with handsomely built hard- 

 wood cabinets of shallow drawers, with perhaps a few glass- 

 topped display cases or a work table with the latest stereo- 

 zoom microscope. 



If this is your first field trip, you look a bit uncertainly at 

 the steep and random spoil heaps with their slippery surface 

 of clay and pebbles. The spiky xerophytic vegetation that 

 is beginning to cover the hills bites you on the ankle. The 

 unshaded sun hammers down on your head and shoulders. 

 You look hesitantly at that dark line in the west, remember- 

 ing that this is "Tornado Alley." You wonder why some 

 people prefer strip mines to the corn fields that were here. 



But look now at some of those pebbles on the hillside. 

 They are red, brilliant in the sunshine. They are sym- 

 metrically shaped, rounded, somewhat flattened. These 

 are ironstone concretions, a thing apart, something special. 

 A drab gray when first dug up by the giant excavating ma- 

 chinery, they redden — it's a kind of rusting — in a year or 

 two as sun and rain and air attack them. When first 

 dumped on the spoil heap, they were still encased in the 

 drab gray shale where they grew an eon ago, formed by 

 interaction of mineral-bearing water and an organic nu- 

 cleus, an animal or a plant. The shale, exposed to weather, 

 has now broken down to the clay of the hills, but the stxirdy 

 concretions remain. Some, you note, have broken in the 

 winter frost and summer sim. You pick one up, already 

 neatly split along its equator. There, in its center, is a 



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