ORTMANN ! TERTIARY INVERTEBRATES. 
323 
entirely different from the extratropical fauna to the north of the tropics. 
This fauna, of course, developed as soon as the climatic differentiation of 
the South Pole offered the necessary conditions, and we may say that for 
a large part of this fauna the shores of the supposed Antarctic continent 
formed the center of origin. Since Miocene Patagonia was apparently a 
part of this center, it is only natural that we should find here indications 
of this Antarctic fauna. 
Some elements of the latter in the Patagonian beds are no doubt the 
ancestors of corresponding forms still living in these regions, and a few 
of them have not changed at all, so that they must be regarded as iden- 
tical species, for instance (compare p. 289): Aspidostoma giganteum, Tere- 
bratella dorsata, Mytilus magellanicus , Infundibidum corrugatum , Infun- 
dibulum clypeolum, Verruca Icevigata , Balanus psittacus. One species, 
Mytilus chorus , is no longer found in southern Patagonia, but has retreated 
a little northward, to Chili. Other species are no longer found in South 
America: Cellaria fistulosa (otherwise almost cosmopolitan), Heteropora 
pelliculata (New Zealand and Japan), Rhynchonella squamosa (Kerguelen 
Islands), Magellania lenticularis (New Zealand). 
In other cases, the fossil and living species are to be regarded as dif- 
ferent, but they are apparently genetically connected. This is the case in 
the following genera (see v. Ihering, 1897 b, p. 532): Voluta , Trophon, 
Turritella , Natica , Venus , Meretrix , Dosinia , Pecten, to which we may 
add Bouchardia. This is especially remarkable in the genus Voluta , 
where three chief types of living Patagonian Volutce, V. ancilla , magel- 
lanica , and brasiliana , have their prototypes in the following species : V. 
dorbignyana , domeykoana and ameghinoi. 
While all these forms are characteristic of the American part of the 
Antarctica, some of them, for instance the Volutce , reappear in similar 
types in Australia and New Zealand. The same is true of Siphonaha 
domeykoana , which does not seem to exist at present in South America, 
but it is still represented in the recent seas of New Zealand in S. dila- 
tata , and analogous are the cases of Struthiolaria , Mal-letia , Sigapatella. 
Struthiolaria is found fossil in South America (Oligocene of Patagonia, 
Miocene of Patagonia, Chili, and northern Peru) and in New Zealand 
(Miocene upward) and still lives in New Zealand, waters. Malletia is 
known fossil from the Miocene of Patagonia, Chili, and New Zealand, and 
living from Chili and New Zealand. Sigapatella is found in the Miocene 
