Here is another species of Brachiopod I picked up from E-bay. The label that came with them said they were "Spirifer whitneyi" from the Lime Creek Formation (U. Devonian)near Rockford, Iowa. However a quick perusal of the "Index Fossils of North America" does not show that species as occurring in the Devonian. My friend Nathan recently posted a series of pictures of Brachiopods that he found in Rockford, Iowa and were IDed by an expert. About half way through the list I found Riqauxia orestes that seemed to match the specimen I had:
A selection of specimens of different sizes.
The above specimens came from the Cerro Gordo member of the Lime Creek Formation, which is Upper Devonian (Fransian) in age.