The character of the Paleocene fauna, its relations to the preceding and following faunæ, and its European correlations are an important part of the evidence on this problem.
The term Paleocene, current in Europe,2 has hardly come into use in this country. As applied here it denotes what we have been calling Basal Eocene, comprising the Fort Union, Puerco and Torrejon, and other equivalent formations older than the Wasatch or typical Lower Eocene. The reasons will appear later for its acceptance as an epoch distinct from the Eocene.
The typical and best known Paleocene fauna is that of the Puerco and Torrejon formations, Nacimiento terrane, of New Mexico. The stratigraphic relations of the faunæ of the four fossiliferous levels of this terrane have been explained by Doctor Sinclair. There is no marked stratigraphic break in the terrane, but there are two distinct faunæ, no species . . .