A 1922 letter from Clemente Onelli to North American paleontologist Elmer S. Riggs, found at Chicago's Field Museum, is one of only a few known first-hand accounts of the former's participation on a fossil hunting expedition along the Río Santa Cruz, southern Patagonia, 1888–1889. Onelli and his companions, who were sent to Patagonia by Francisco P. Moreno, director of the Museo de La Plata, were among the first to collect fossil mammals at this important locality. Moreno had first discovered fossil mammals there in 1876–1877. He then sent Carlos Ameghino, who worked as an assistant preparator of palaeontology at the museum, to revisit his discoveries in January 1887. Ameghino later lost his position at the museum over a dispute between his brother, paleontologist Florentino Ameghino, and the director, in March 1889. Onelli, who had only been associated with the Museo de La Plata for a few short months, was asked by Moreno to accompany a new expedition outfitted in 1888–1889. In December 1922, Riggs travelled to South America to make a representative collection of the fossil mammals of Argentina and Bolivia. Learning of his arrival in Buenos Aires, Onelli wrote him a letter, in Spanish, providing detailed information about fossil localities along the Río Santa Cruz. This letter, translated here, along with the accompanying sketch map, provides previously unknown details about Onelli's itinerary and his observations.
Archaeology of South America / by J. Eric Thompson, Division of Historical Research, Carnegie Institute of Washington. Formerly Assistant Curator of Central and South American Archaeology, Field Museum. 12 plates, 18 text figures,
