Here are some Goniatites from the Mahantango formation of Pennsylvania. These were all found in the Sherman Creek member, which used to be called the Upper Frame Shale member, at a site near the village of Seven Stars in Pennsylvania. I find what appears to be two different genus:
A 2-3 cm variety:
And a 6-7cm variety:
The smaller I think is Tornoceras but it's hard to see the suture lines to confirm. The larger seems to be Agoniatites. It's hard to get a firm ID on these as there is very little information published on the Goniatite genera from the Mahantango. Agoniatietes is the only genus that is listed in the "Fossil Collecting in Pennsylvania" book which is the best reference for anyone looking for fossils sites in PA. The next best reference is "Stratigraphy and Paleontology of the Mahantango Formation in South Central Pennsylvania" and that book does not discuss them at all. This could be because they are rare fossils to find in the Mahantango and, truth be told, I've only found them at one site. In any case, Tornoceras and Agoniatites are the two most common genera in the Middle Devonian so it might be safe to use them to ID what I have found.