324 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 



of Patagonia and Chili, from the Oligocene upward in New Zealand, and 

 lives in New Zealand waters. Perhaps we may put into this category the 

 subgenus Cominella of Buccinum, which, although known fossil in the 

 northern hemisphere, is at present confined to the southern, the metrop- 

 olis of the typical species being New Zealand (see Tyron, 1881, p. 201). 

 Finally, in Terebmtella dorsata, we have a species that in the fossil 

 state is common to New Zealand and Patagonia, while at the present 

 time it is extinct in New Zealand, but survives in Patagonia. 



Thus we see that, in the Miocene Patagonian beds, we must distinguish 

 two chief faunal elements : a tropic-subtropical one, which shows relations 

 to the tropical parts of the rest of the earth (and through these with the 

 subtropical faunas of the northern hemisphere, in Europe and North 

 America), and an antarctic element, which is peculiar to the southern 

 hemisphere, and which shows relations only to the faunas belonging to or 

 connected with ancient Antarctica. The first element was the chief factor 

 that enabled us to compare the Patagonian beds with deposits of the 

 northern hemisphere, and thus to ascertain their age, while the other has 

 given us valuable hints for the comparison with New Zealandian and 

 Australian beds. 



For the later history of the Patagonian marine fauna the Cape Fair- 

 weather beds are valuable. While their fauna shows on the one side a 

 continuation of Patagonian types (see p. 307), we have here, on the other 

 side, an introduction of new forms. These new elements are possibly in 

 large part new immigrants from the Antarctic shores, and, as v. Ihering 

 (1897 b) urges, this immigration from the south must have continued on 

 a large scale almost up to the present time, at least to the Pleistocene. 

 This later introduction of Antarctic elements is the most important change 

 in the general character of the fauna that has taken place since the time 

 of the deposition of the Patagonian beds, and is in connection with the 

 retreat of the tropical elements toward the north the most prominent 

 feature that distinguishes the present Patagonian, Magellanian, and Chilian 

 faunas from the fauna that lived on the shores of ancient "Archiplata." 



