Here is the fossilized remains of an Ordovician cephalopod about 7 cm long. It was found in June 2008 at the Bardstown Road cut, outside of Louisville, Kentucky.
It is not in the best of shape. By the looks of it once the creature died its shell was exposed on a sea bottom for a while and was worn a bit by the environment.
The milestone of this piece is that I counted 20 segments on it and that is the most I ever found on a cephalopod fossil.
Identifying this cephalopod could be a problem since it is a mold and does not have siphuncle showing. Looking at a 1955 Ohio Fossils book it refers to the species Endoceras proteiforme or Orthoceras dyeri as common Ohio Ordovician cephalopods. I do not think those genus names are used anymore though.
The Ohio Fossils book from 1996, it says that Cameroceras inaequabile (Miller) used to be identified as Endoceras and is most commonly found in Ordovician rocks in Ohio. In the next paragraph, it said that Treptoceras is the most common cephalopod found in Ohio Ordovician rock.
So maybe this specimen was one of those species.