Tentatively Piranha & Teres, from TFF are thinking this is a Beloitoceras. However, they have never been found in the Galena Formation according to Caleb. I got it out, story to come, and he has offered to prep it and get a solid ID. Apparently, since this is a mature specimen, it is a rather important find!
Here is a link to a great pdf from the USGS for identifying cephalopods!
http://pubs.usgs.gov/pp/1066p/report.pdf
Thanks Teres from TFF!