24 THE DESEADO FORMATION OF PATAGONIA 
their dentition, which is adapted to browse. Whether they 
lived on soft or hard ground is not known, as the feet are 
not known in any case but the Homalodontotheridae, where 
they are five toed and adapted to soft ground. Such large 
animals were probably inhabitants of some river bank. 
The rodents do not contribute much in the determina- 
tion as to the type of the country, for they could have lived 
in the open or in the wooded country, but their relative 
abundance is rather typical of open country. 
The birds are. all running birds, and indicative of the 
country having been an open one. 
Of our fauna If per cent were flesh or insect eating, and 
for the purpose of determining the type of country may best 
be omitted. The rodents could have been either forest or 
open country forms. Of the remaining 54 per cent, the 
typotheres, the litopternas, the Rhynchippidae, the Leon- 
tinidae, the nesodonts and the birds (46 per cent) were 
distinctly adapted to live on hard ground; the other 8 per 
cent being evidently suited to living near a river. All 54 
per cent ate either grass or browse. The litopternas are 
grass eaters; the typotheres were specialized to eat grass 
or bark; nesodonts, Leontiniidae, and Rhynchippidae are 
grass and browse eaters. Even the Pyrotherium has a pair 
of gnawing tushes. The picture arising from these con- 
siderations is a bush covered prairie, a country not unlike 
the upland bush pampas of Patagonia today. 
There is not an aquatic form (fish or turtle) in the whole 
list, so it is evident that the stream which deposited these 
Deseado beds was not abundantly inhabited. To me it 
looks like so many of the streams in an arid country, dry 
through a considerable part of the year, and so uninhabited. 
In the whole list | see nothing to indicate forests or swamps. 
The arid bush covered plain alone seems to suit the re- 
quirements. 
As I see this fauna it is composed of several distinct 
elements, representing different invasions and an ele- 
