324 
PATAGONIAN EXPEDITIONS : PALEONTOLOGY. 
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 Buccimtm, 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 Terebratella 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.” 
