The intention of this work is to revise all mammal remains found in Switzerland from the Eocene period and to discuss the changes in the European mammal fauna during this time period based on this revision. I choose to present my findings in the form of a material catalog because it has advantages that are particularly significant for an object like mine: it compels the observer more than any other format to provide a thorough account of all documents, including those that are inconspicuous and inconvenient, and ensures that the individual, the only real entity we are dealing with, receives its due recognition, rather than disappearing under the guise of abstractions, species, and genus. This book is an unaltered reprint of the long out-of-print original edition.