Transcriber’s Notes: Underscores “_” before and after a word or phrase indicate _italics_ in the original text. Equal signs “=” before and after a word or phrase indicate =bold= in the original text. Small capitals have been converted to SOLID capitals. Illustrations have been moved so they do not break up paragraphs. Old or antiquated spellings have been preserved. Typographical and punctuation errors have been silently corrected. [Illustration: The skull of Pyrotherium sorondoi Ameghino. ⅛ natural size. See page 175.] The Deseado Formation of Patagonia Frederic Brewster Loomis, Ph.D. _Professor of Comparative Anatomy Amherst College_ [Illustration] EIGHTH AMHERST EXPEDITION 1911 PUBLISHED UNDER THE AUSPICES OF THE TRUSTEES OF AMHERST COLLEGE 1914 _Copyright, 1914_ BY FREDERIC B. LOOMIS THE RUMFORD PRESS CONCORD · N · H · CONTENTS CHAPTER PAGE I. Organization of the expedition—history of the work done in the Deseado formation 1 II. Description of the Amherst locality—age of the overlying beds—age of underlying beds—age of Deseado 6 III. Table of the animals—study of the feeding habits— character of the habitat—the origin of the elements of the Deseado fauna 19 IV. Systematic arrangement—the Litopterna, Eoproterotherium, Notodiaphorus, Deuterotherium, Protheosodon, Coniopterotherium, Tricoelodus, Proadianthus 28 V. Typotheria, Archaeohyrax, Plagiarthrus, Prohegetotherium, Prosotherium, Propachyrucos, Phanophilus, Archaeophylus, Eutrachytherus, Argyrohyrax, Isoproedrium 53 VI. Rhynchippidae, Toxodontia, Rhynchippus, Morphippus, Eugeniops 86 VII. Leontinirdae, Leontinia, Ancylocoelus 108 VIII. Nesodontidae, Proadinotherium, Pronesodon, Coresodon, Interhippus, Nesohippus 122 IX. Isotemnidae, Trimerostephanus, Pleurocoelodon, Lophocoelus, Henricofilholia 129 X. Homalodontotheria, Asmodeus 134 XI. Astrapotheria, Parastrapotherium 142 XII. Pyrotheria, Pyrotherium 156