Boundary in South America. 27 



the terrestrial deposits, which contain the most ancient 

 mammals of Patagonia, Outside the limits of the San 

 Jorge-Sea (which means in large parts of Patagonia, as 

 will be proved in Part III) the mammal-bearing strata 

 rest directly on the chief dinosaur-bearing horizon, the 

 Pehuenche Beds, and the hiatus separating both forma- 

 tions may easily be overlooked. The case already 

 studied in the region of Confluencia thus repeats itself. 

 The normal sequence of strata is preserved chiefly in the 

 marginal regions of the present Patagonia and is repre- 

 sented by the Pehuenche-San Jorge-Casamayor and 

 Deseado. 60 



The cases instanced by Ameghino may be briefly 

 reviewed. The section from the southern shore of Lake 

 Colhue Huapi, 67 with the association of mammals, turtles, 

 serpents and dinosaurs in the same layer of the Noto- 

 stylops Beds, has been mentioned. Further, Ameghino 08 

 cited Roth as witness to strengthen his own assumptions, 

 and Roth himself mentioned the occurrence of dinosaurs 

 with Notostylops. 69 According to the statement of 

 Ameghino, remains of Genyodectes serus A. S. Woodw. 

 have been found by Roth about 30 feet above a layer with 

 mammals of the Notostylops-fauna. In the same man- 

 ner the great turtle, Miolania argentina A. S. Woodw., 

 appeared in a locality about two miles north of Lake 

 Colhue Huapi together with the same fauna of mammals. 



It seems to me remarkable that the contemporaneity of 

 dinosaurs and Notostylops-fauna, has been put forward 

 in the above mentioned reports, but the finding of 

 Pyrotherium together with dinosaur bones has never 

 been confirmed. No study or work in reference to the 

 Pyrotherium Beds in Patagonia has ever been more 

 thoroughly gone into than by the Amherst Expedition, 

 and therefore it is of fundamental importance that Loomis 

 flatly denies the association of dinosaurs and the Deseado 

 fauna. This seems to indicate that the Cretaceous rep- 

 tile fauna sent some survivors into the time of the Noto- 

 stylops Beds (Casamayor), but these remains did not 

 last up to the time of Pyrotherium. It is impossible to 



00 It seems to me convenient to apply the denominations Casamayor and 

 Deseado for the Notostylops, Astraponotus and Pyrotherium Beds, as has 

 been done by Loomis, following the example of Tournouer and Gaudry. 



67 Les formations sedimentaires, p. 112, fig. 31. 



68 Ibidem, p. 80. 



60 Beitrag zur Gliederung der Sedimentablagerungen in Patagonien und 

 der Pampasregion, N. Jahrb. Min., Beil.-Bd., 26, p. 95, 1908. 



