2 THE DESEADO FORMATION OF PATAGONIA 
trips covered the country from Chubut down to the 
Straits of Magellan, and the various formations from the 
Lower Cretaceous to the Pampean or Pleistocene. Carlos 
Ameghino and his brother, Florentino, for years explored 
in Patagonia, going summer after summer at their own 
expense, and in the meantime maintaining a small book 
and stationery store in La Plata, the profits of which gave 
the two brothers a living and furnished the funds for the 
continual expeditions. In the back of the store was the 
workshop from which came the continuous stream of 
knowledge in regard to these strange faunas. One of the 
best pieces of work done by the brothers was the collect- 
ing and describing of the fauna of the Pyrotherium beds 
the bulk of which is contained in two papers entitled, 
Premiére Contribution a la Connaissance de la Fauna 
mammalogique des Couches a Pyrotherium, and Mammi- 
feres Crétacés de l’Argentine, Deuxiéme Contribution, etc., 
both published in the Boletin del Instituto Geografico Ar- 
gentino, tomes 15 and 18 respectively. These two papers 
give names to most of the forms which we found, but the 
genera and species are based on very fragmentary and in- 
complete material. It has been a pleasure to find the accu- 
racy with which these descriptions were made; and our part 
has been chiefly to supplement and increase the knowledge 
of the various forms, and to determine from the more 
complete material the relationships of these strange forms. 
In some cases we have been able to assemble all the parts 
of the animals, and in the others to add more or less to the 
completion of the knowledge of the forms. There is one 
perculiarity of Ameghino’s descriptions, namely the ab- 
sence of data as to the localities where the forms were 
found. 
About 1900 Tournier, in the interests of the Paris Mu- 
seum, made a series of expeditions (5) to Patagonia, on 
some of which he found a Pyrotherium, or as he has termed 
it Deseado, locality just south of the Deseado River, 
