116 ANALES DE LA SOCIEDAD CIENTÍFICA ARGENTINA 



passing quite through the Guaranilic and Lower Lignite beds and 

 intotherocks oí ihe VariegatedSandstones, maynowbeseeninmany 

 Jocalities filled with a senes of Tertiary deposils varjing in age 

 frorn earlj Eocene to Pliocene. Such deposits have been sometinnes 

 oí marine, sometimes of fresh-water or aéolian origin. Tiiecomplex 

 nature of the stratigraphj of the región in which they now occur, 

 due to the eroded nature of the surface upon which they were laid 

 down, has led Dr. Ameghino to consider such Tertiary deposits as 

 interstratified with the GUaranitic beds and Variegated Sandslones 

 and thereforeof Cretaceous age. Formerly Dr. Ameghino considered 

 all of such Tertiary deposits as of one age and belonging to one series, 

 which he designated as the Pyrotherium beds. In my former paper 

 Ipointed out that in the Pyrotherium beds of Ameghino there were 

 represented two or more distinct horizons. I at the same time 

 suggest that some of the fossil mammals described by Ameghino as 

 from the Pyrotherium beds appeared lo belong to a formation more 

 recent than the Sarita Cruz beds. Further explorations in Palagonia 

 have only contirmed my former views and Dr. Ameghino has since 

 partially adopted these views. He has now divided his Pyrotherium 

 fauna into Iwo faunas, referring one to the Middle ant the other to 

 the Upper Cretaceous. Unfortunately he has not yet recognized the 

 true stratigraphic position of the beds in which the various faunas 

 were found with refereuce lo the Guaranitic beds. A further subdi- 

 visión of ihis Pyrotherium fauna is necessary and a recognition of 

 the Miocene, Pliocene and Pleistocene nature of severa! oí the forms 

 included in it. Among such Pleistocene forms will be found the 

 large gravigrade edentate described by Ameghino as not disliii- 

 guishable from Mylodon and more than likely Pyrotherium, which 

 resembles very closely some of the larger Pleistocene herbivorous 

 marsupials of Australia. Unfortunately I have not as yet been able 

 to lind any remains of Pyrotherium and have^ therofere, been 

 unable to determine its exacl stratigraphic position. It is interes- 

 ting to note, however, that Dr. Santiago Roth, who has spent two 

 years collecting in beds wich according to Ameghino contain his 

 Pyrotherium fauna, has not íound a single íragment of Pyrothe- 

 rium, though Ameghino says that Pyrotherium is the most abundant 

 and most characteristic fossil in the beds. Dr. Roth found other 

 fossils of the Pyrotherium fauna fairly abundant. 



« The Pyrotherium beds. as that term has been used by Dr. Ame- 

 ghino, includes a series of deposits oí yarying age from Eocene to 



