This publication pulls directly from the 1926 Marshall Field Paleontological Expedition conducted in the province of Catamarca, Argentina. This expedition made extensive collections of mammal fossils from the Araucanian formation in the region, totaling some 200 specimens, including carnivorous marsupials and previously unknown items. Originally published in 1934, this robust report provides an invaluable resource to 20th century American paleontology and taxonomy.