CHAPTER X 



Results of Expedition 



After the preceding running narrative I should like to 

 sum up the general results of the expedition as they appear 

 after a preliminary survey of the material, now that it is 

 all together. It is to be understood, however, that these 

 are not final, such conclusions being only possible after a 

 more complete study of the details of the collection. Such 

 final results together with the bases for arriving at them are 

 to be published later as the second volume of the report 

 of this expedition. 



First, as to the age of the beds in which most of our work 

 was done. The difficulties in the way of determining this 

 easily are mostly in the fact that all the numerous remains 

 of mammals, birds, fishes, and shells belong to species and 

 genera known from no other part of the world. The stra- 

 tum best suited for comparisons is the one which carried 

 the large oysters and to which I have always referred as 

 Patagonian. From it we collected some 3,000 shells be- 

 longing to over fifty species. By Ameghino this bed was 

 first called Patagonian, and later divided into "Supra- 

 Patagonian, Juliene and Leonense" and assigned to the 

 first part of the Eocene (3,000,000 years ago). Ortmann 

 after a very careful study of the shells collected from it by 

 the Princeton Expedition concluded that there was but one 

 layer, the Patagonian, and that the other names repre- 

 sented only local phases of the bed; and that its age was 

 Lower Miocene, a whole geological age later. Von Ihering 

 and Scharff have adopted Ameghino's conclusion as to the 

 age, but in spite of the difficulties of the shell evidence 

 Ortmann's determination seems to me correct. Then in 

 addition to that evidence there have been found in it 



