Upper Mississippian Faunas of Western Montana

The author has made a study of an assemblage of fossils from the Blacktail Range near Dillon Montana with the purpose in view of attempting a correlation of that group with the fauna of the Big Snowy Group. Fossils have also been obtained from a limestone formation in northwestern Montana and from four different areas in the Amsden formation in central and western Mont­ana.

Rugose Corals of the Madison Group

One of the best types of index fossils, and one which occurs most plentifully in the Madison group of formations in Montana, and yet, one which has been little studied, is the group of rugose, or cup, corals. Perhaps this group of fossils has not been studied in detail because their distinguishing characteristics are mainly internal, and labo­ratory preparation in the form of thin section or polished surfaces is necessary to bring out these characteristics.