One of the more common brachiopod fossils from the Devonian is Athyris and they can be found at Arkona as well. Below are some Athyris spiriferoides shells from the Hungry Hollow member of the Widder formation.
Edit 01/17/14: I now think that the above specimen is A. vittata while the below specimen is A. spiriferoides
While not as large as those found in the Wanakah shale (which is roughly equivalent to the Widder) they still show the typical concentric growth lines which mark this species. Those that I have found, within the Hungry Hollow member of the Widder, are often flattened or crushed. Hopefully one day I will find an inflated specimen.