ii4 STUDIES IN GEOLOGY, No. 4 



Before discussing the age of the plant beds, I wish to refer 

 to the so-called Patagonian beds of southern Argentina, the 

 marine fauna from which has been admirably described by 

 Ortmann. 22 This fauna has been satisfactorily shown to be 

 of lower Miocene age, and while the Australian and New 

 Zealand element is more pronounced than, in the Navidad 

 beds, nevertheless the Patagonian has, out of a total fauna 

 of 175 species, 34 that are identical with and 15 additional 

 that are closely allied with Navidad species. Ortmann quite 

 rightly concludes that the Patagonian is synchronous with 

 at least a part of the series referred to the Navidad. Two of 

 the Chilean species are common to the lower Miocene Heath 

 stage 23 of northern Peru and there are an additional number 

 of closely related species in the latter, according to Grzy- 

 bowski, but both the determinations and horizon of this 

 author are questionable. 



A more comprehensive study of the lower Miocene fauna 

 of Northern Peru by Spieker in No. 3 of these Studies, 

 discusses fully the few relationships and many differences 

 between the Navidad fauna and that of the same age in Peru, 

 and suggests the presence of an intervening Pacific land mass 

 to account for the lack of intermigration between the two 

 areas. 



Whether the Chilean fauna be regarded as lower or 

 middle Miocene it is evidently undoubted Miocene and very 

 probably earlier Miocene. I see no reason for not corre- 

 lating it with the Burdigalian stage of European geology 

 and with the Patagonian beds of Argentina. The fossil flora 

 is more remote from fossil floras of known age to afford as 

 satisfactory data for its correlation. It is in my judgment 

 not appreciably older than the associated fauna. A feature of 

 great interest is the presence of a more northern element 



23 Ortmann, A. E., Tertiary Invertebrates. Princeton Exped. to 

 Patagonia, vol. 4, pp. 45-332, pis. n-39, 1901-1906. 



23 Grzybowski, J., Neues Jahrb. Beil. Bd. 12, pp. 610-664, pis. 

 15-20, 1899. 



