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 1 1 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 I 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- 



