Stratigraphy and fauna of the Sacajawea Formation, Mississippian, of Wyoming

The lower part of the Amsden is Mississippian in age and is here described and named the Sacajawea formation to separate it from the upper part of the Amsden (Pennsylvanian). Thirty-one species are added to the known fauna, of which eleven are new. The new species belong to the genera Clionolithes, Spirorbis, Rhipidomella, Chonetes, Linoproductus, Streptorhynchus, Selenella?, Composita, Euphemites, Conocardium, and Griffithides.