286 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. 



ing of the marine Magellanian beds and the Upper Lignites (see Ort- 

 mann, 1898, p. 481 and 1899, p. 457, and Hatcher, 1900 a, p. 97). 

 At the top, the Patagonian beds pass gradually into the typical Santa- 

 cruzian beds containing Mammalian remains, which, at their base, are 

 sometimes interstratified with the uppermost Patagonian beds (Hatcher, 

 1900 a, p. 105). The contact of both has been observed: in the region of 

 the upper Rio Chalia, Arroyo Gio, Lake Pueyrredon ; interstratification 

 has been observed in the Canon near Sierra Oveja, Rio Chico. 



THE AGE OF THE PATAGONIAN BEDS. 



i. COMPARISON OF THE PATAGONIAN FAUNA WITH FAUNAS OF THE 



NORTHERN HEMISPHERE. 



The conflicting opinions as to the age of the Patagonian beds have been 

 shortly mentioned by Mr. Hatcher (1900 a, p. 103). For the sake of 

 completeness we give here the different opinions of the various writers. 



Darwin (1846, pp. 118 and 134) believes them to be older Tertiary, 

 probably Eocene. 



DOrbigny (Cours elementaire de Palontologie et de Geologic, v. 2, 



"1852, p. 750) puts them in his Falunien stage (Miocene], but it should be 



remembered that D'Orbigny's material came chiefly from the northern 



parts of Argentina (Entrerios, Rio Negro), and it seems that these beds 



are much younger. 



The position in the older Tertiary, without reference to any particulars, 

 has been the accepted one afterward. 



Doering (1882) was the next to take up this question, but he was much 

 handicapped by a serious mistake as to the proper succession and corre- 

 lation of the different deposits of Patagonia. He uses the term " Pata- 

 gonian formation " for a series of marine and freshwater beds, which he 

 places in the Oligocene and Upper Eocene. It is hard to say which of his 

 three subdivisions (Piso Paranense, Mesopotamico, and Patagonico) cor- 

 responds to actual deposits, since in all three of them apparently different 

 faunas are confused, but, as far as can be made out, the Piso Paranense 

 has for its type what is now called by the same name (Entrerios), the 

 Piso Patagonico includes the classic locality for the marine Patagonian 



