These brachiopods are the Onniella (Dalmanella) quadrata of the Maquoketa Group of Eldorado, Iowa. The animals lived in the Late Ordovician period. These brachiopods are similar to the ones found east of Louisville, Kentucky in the Kope Formation. See my posting about the Dalmanella multisecta: CLICK HERE
According to the write up on the Kope Formation on Wikipedia, it is part of the three formations that make up the Maquoketa Group. So the Iowa fossils appear to have some relationship with the Kentucky fossils.
These fossils were bought from eBay seller timfossil2001 who has some nice deals on Minnesota and Iowa fossils: http://www.ebay.com/sch/timfossil2001/m.html?item=370559137286&viewitem=&_trksid=p4340.l2562
