LOCALITIES 2S 
from which he gathered a considerable collection which 
has been described by Albert Gaudry in various papers 
‘mostly in the Annales de Paléontologie. 
These two collections and their collaborations represent 
all the work thus far done on the Deseado beds and fauna. 
Our collection is the first one of any considerable size to 
be brought to North America, and it seems to be by far the 
most complete, the various animals being represented by 
more complete skeletons than in any of the previous col- 
lections. 
The beds were first designated as the Pyrotherium beds, 
and are always so referred to by F. Ameghino. Tournier 
and Gaudry, feeling the prejudice which is fairly general 
among Palaeontologists against names based on any con- 
tained animal (which may or may not be present at other 
localities, which may extend through more than one 
period, and whose name may be changed as a result of 
further knowledge) used the term Deseado formation, as 
his collections came from the neighborhood of this river. 
This is a geographical name and avoids the chance for 
confusion; so I have adopted it throughout this paper, it 
being understood as an equivalent of the term Pyrotherium 
beds. 
Ameghino never gave the exact, or anywhere near the 
exact, localities from which his Deseado specimens came. 
It was not until 1906, when his Formations Sedimentaires* 
appeared, that any localities were designated, and there 
on a sketch map he indicates as Deseado exposures, about 
a dozen points, scattered between the upper part of the 
Chubut River to some 25 miles south of the Deseado 
River. These are included in an oval area some 500 miles 
long by 150 miles wide. Ameghino also suggests on this 
occasion that the Deseado formation originally extended 
over at least the whole of this area. As will be seen in the 
next chapter, I believe that the deposits of this age 
* Anal. Mus. Nac. Buenos Aires, ser. 3, t. 8, p. 99. 
