THE DESEADO FORMATION OF PATAGONIA 
CHAP ie 
INTRODUCTION 
THE material described and the conclusions drawn 
in the following pages are the results of the Amherst Ex- 
pedition to Patagonia in 1911; 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 ’11, Waldo Shumway ‘12, and William 
Stein of St. Joe, Wyoming, and left Amherst July 1, tort, 
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 
