140 HUNTING EXTINCT ANIMALS 



the Cretaceous, but to my mind even more probably from 

 North America in the Cretaceous. What Ameghino con- 

 sidered Primates have been assigned to these marsupials, 

 and the few specimens which we found, belonging to the 

 type known as "Primates," clearly fall into this group of 

 marsupials. This leaves as an unsettled problem the or- 

 igin of the South American monkeys. 



The fossil woods which we found have not been studied, 

 and when this is done they should throw some light on the 

 age of the beds in which they occur, and especially on the 

 type of climate under which they grew. The abundance 

 of this wood is striking and would indicate a heavily forested 

 region for its source. 



Considering the peculiar character of the dentition of 

 so large a proportion of the animals which have come from 

 these early South American beds, two features are striking : 

 the tendency to develop gnawing types of front teeth, 

 similar to rodent types, and the tendency to develop teeth 

 which grow permanently. Both these features are different 

 from grass feeders, or feeders on soft vegetation. The Pat- 

 agonian pampa today is covered with bushes, and the 

 wild animals have to eat largely the twigs and ends of the 

 branches. It seems to me that the chief food of the above 

 forms must also have been woody. It is this line of thought 

 which we apply to the rodent to explain its type of denti- 

 tion, and it seems proper to carry it over to these other 

 groups which have in so many respects similar structures. 

 If this be a fair deduction we must think of the ancient 

 country as covered with a scrub brush which, while pro- 

 viding plenty of food, gave it in the least usable form, 

 requiring for mastication powerful dental development. 



One other feature is notable in the animals of this fauna, 

 and that is the presence of large numbers of birds' bones. 

 The largest of these is a femur four inches in diameter, 

 which must have belonged to a running bird equal in size 

 to the extinct monsters of New Zealand and Madagascar,. 



