6 PROCEEDINGS OF THE NATIONAL MUSEUM vol.73 



distribution shows 4 of the 16 species are identical with forms de- 

 scribed by Dusen from these zones in the Straits of Magellan region 

 and two additional are identical with forms described by this author 

 from the Seymour Island Tertiary, the present occurrence repre- 

 senting their most northern known range. This may be stated in 

 another way by saying that in the time immediately preceding the 

 Patagonian transgression a humid and fairly cool temperature flora 

 extended between 41° and 54° south latitude. Since I regard the 

 Patagonian transgression as corresponding approximately to the 

 Burdigalian stage of the European Miocene, it would mean that 

 the Lago Nahuel Haupi fossil flora should be correlated with the 

 lowest Miocene or the Oligocene of the Northern Hemisphere. Al- 

 though denominated cool temperate, it is clear from its great north 

 and south range and its possible extension to Antarctica that the 

 climate at that time differed from that of the present in its greater 

 uniformity and relative greater mildness in the far south. 



The florule found at two localities on the upper Rio Chalia is 

 markedly distinct from the other, not only in representing entirely 

 different genera but in lacking any species common to the Araucaria 

 or Fagus zones. It has, moreover, a species common to the Santa 

 Cruz (?) flora of Mirhoja in Chubut Territory. As already men- 

 tioned, the plants have their modern relatives far to the northward 

 of their fossil occurrence, and the leaves are individually much 

 larger than any in the Rio Negro florule. They tV.us represent an 

 occurrence of warm temperate types in latitude 49° south. Hatcher 

 describes lower Patagonian marine beds from the upper Rio Chalia, 

 and, so far as chronologic terms are concerned, there is little choice 

 between the terms Patagonian and Santa Cruz, since I l^elieve the 

 latter, although partly contemporaneous with the Patagonian, 

 extends upward to a somewhat later time. 



Although the evidence is far from conclusive, it points to this 

 florule being considerably younger than the other, and to its early 

 Miocene age. The location of both this and the earlier florule are 

 shown on the accompanying sketch map, the base of which is Wind- 

 hausen's map, showing the marine transgression of the Patagonian. 

 I have also indicated the location of the Santa Cruz (?) plant local- 

 ity at Mirhoja in Chubut Territory. 



It will be noted that the localities in the vicinity of Lago Nahuel 

 Huapi, which I regard as belonging to the pre-Patagonian Araucaria 

 and Fagus zones, lie in an area which was transgressed by the mar,ine 

 waters of the long gulf depicted by Windhausen, that the localities on 

 the upper Rio Chalia are interbedded in its marginal deiDosits, and 

 that the Mirhoja locality, which I referred to the Santa Cruz, lies to 

 the eastward of the Patagonian Gulf and was presumably a low-lying 



