— 379 — 
We have largely failed in the proper interpretation 
of these analogies because of our attempt to explain 
them from a single standpoint. In reality it is a com- 
plicated problem in the solution of which, according to 
Ortmann, these conditions must be taken into conside- 
ration, namely. (1) The migration of artic litoral forms 
via the cold strata of the deepsea to the Antartic zone 
and vice-versa. (2) The gradual adaptation of once wide- 
ly distributed genera to the conditions of high latitudes, 
(3) Migration along the Pacific coast of America and 
along the west coast of Africa. 
| The last explanation, proposed at the same time by 
Bouvier and Ortmann, is contradicted by the fact that 
wholly different faunas succeed each other along the Pacific 
coast of America, and finds no support through what 
we know concerning the Pleistocene Molluses of California 
and Chile. 
All these explanations have entered upon a new era 
through the foregoing investigations which in the place 
of the hypotheses, furnish a substantial foundation for 
the historical development of the Magellan fauna. Those 
investigators who are engaged in the study of the dis- 
tribution of marine animal groups that offer little 
Palaeontological material will not fail to follow with 
interest the results here obtained. 
One more point may be mentioned. The presence of 
subtropical genera like Perna, Ficula, Seutella, etc. in 
the Patagonian Tertiary leaves no doubt that a consider- 
ably warmer climate then existed in this region, which, 
according to my calculations, amounted to about 20 
degrees. That the same conditions obtained in Navidad, 
is shown by the presence of the genera Conus, Mitra, 
Oliva, Terebra, Lucina, Avicula. 
This point is important because many geologists 
bring forward as an argument for the Wathorst Theory 
of the ‘shifting of the Pole during the Tertiary period 
the relatively cold climate of Chile which we see is 
