A study of the Upper Pennsylvanian and Lower Permian stratigraphy and fossils has been in progress by the writer for some time. This study has involved the correlation of the beds of these systems over North America and Eurasia, in so far as that is possible. It has particularly involved the correlation of the Appalachian and western sections, and in view of some novel suggestions that have been made to account for the peculiar distribution of the fossil air-breathing vertebrates, it is thought that the results of this work may be of interest.
The invertebrate fauna of the upper part of the American Pennsylvanian has certain characteristics. For instance, the fauna, as a whole, possesses unity of expression and is characterized by relatively little evolution when the great length of time involved is considered. The larger formations, or stages, . . .