THE DESEADO FORMATION OF PATAGONIA 



CHAPTER I 



Introduction 



The material described and the conclusions drawn 

 in the following pages are the results of the Amherst Ex- 

 pedition to Patagonia in 191 1; an expedition organized 

 and sent out by the Class of '96 as a part of their fifteenth 

 reunion. The party consisted of Frederic B. Loomis '96, 

 Phillip L. Turner 'n, Waldo Shumway '12, and William 

 Stein of St. Joe, Wyoming, and left Amherst July 1, 191 1, 

 returning the first of February the ensuing year, having 

 spent its time collecting in the early Tertiary beds of 

 Patagonia, as exposed in the Territories of Chubut and 

 Santa Cruz, the aim being to secure from the earlier periods 

 a fuller knowledge of the vertebrate animals, such as the 

 Princeton Expeditions obtained for the Patagonian and 

 Santa Cruz formations. The narrative of the expedition 

 has been told in "Hunting Extinct Animals in the Pata- 

 gonian Pampas." 



Material was found in various beds, from the Creta- 

 ceous up to the Lower Miocene; but the major part of 

 the fossils, and most of the facts new to science came from 

 the work in the Deseado Formation. The collections 

 from the horizon were so complete and interesting that 

 this report of the expedition has assumed the form of a 

 monograph of the Deseado Formation, otherwise known 

 as the Pyrotherium beds. 



The first work in this formation was done by Carlos 

 Ameghino who at various times between 1889 and 1894 

 collected for his brother, Florentino Ameghino, the latter 

 studying and describing the collections of Carlos, whose 



