The ubiquitous Pseudoatrypa makes an appearance in the rocks of the late Devonian (Fransian stage) Lime Creek formation of Iowa. It gets fairly large, as is typical of the genera,and a little wider than some.
There is another species which looks very similar to Pseudoatrypa called Independatrypa independensis which has since been reclassified as Desquamatia (Independatrypa) independensis by Williams et al. in 2002. It's found in the Cedar Valley formation which is late Givetian stage of the Middle Devonian in Iowa.
Some grew to very large proportions
Sample of the largest Desquamatia (Independatrypa) independensis I have with a typical Pseudoatrypa.
All the specimens shown above were purchased from this seller on E-bay.