294 PATAGONIAN EXPEDITIONS: ZOOLOGY. 



men to Chili and the La Plata district, such as Unio, C/ii/iua, Parasfaciis, 

 ySg/ca, etc., including many species and even their parasites [Temnoce- 

 phahi). which are identical on both sides of the Andes. This contrasts 

 sharply with the Archamazonian fauna, as tropical genera extend to Rio 

 Plata and Rio Negro, which are completely wanting in Chili and Peru. 

 In Ecuador, however, the Cordilleras form no such zoogeographical division, 

 due certainly to differences in the geological history of both parts of the 

 Andes. * * * These facts point out that the invasion of the Archama- 

 zonian element into Archiplata is quite a recent one. The intrusion of the 

 Archamazonian element is Pliocene or post-Tertiary, and the Andes 

 formed a barrier insurmountable to fresh-water crabs and mussels as well 

 as to fishes, chelonians and alligators. 



"It is evident that the two faunal elements of South America corre- 

 spond to geographical districts which were separated by the ocean during 

 the greater part of the Tertiary. The intermixture of the two elements, 

 and especially the intrusion of Bolivian ants, land snails, etc., in Eastern 

 Brazil is by no means finished, but is a fact which we observe to-day. * * * 



"In relation to the ancient connection of Africa and Archamazonia I 

 have given arguments (1890) in favor of a Mesozoic ' archiatlantic conti- 

 nent,' which existed during the earlier Tertiary. 



"At first because of some paleontological facts noted by Schlosser, I 

 believed that this continent could have transmitted Eocene mammals from 

 South Africa to Europe, an idea now defended by Ameghino and Osborn ; 

 but in 1893 I modified my opinion and set forth the hypothesis that no 

 Eocene placental mammals had existed either in Archamazonia or in 

 Ethiopian Africa. The ancient continent uniting Archamazonia with 

 Africa I named Archiatlantica in 1890, using in 1892 the term Helenis, 

 and in 1893 that of Archhelenis, with the purpose of preventing confusion 

 with the ' Atlantis ' a hypothetical land bridge between South Europe and 

 Central America proposed by Unger. 



"The intimate relations between the fresh-water faunas of Africa and 

 Brazil, and the colossal difference which exists between the fresh-water 

 faunas of Archamazonia and Archiplata, prove that both territories during 

 the greater part of the Tertiary were separated quite as completely as the 

 two Americas. In this case the mammalian fauna of Patagonia may have 

 reached Ecuador or Columbia by means of the upheaval of the Andes, 

 but not Brazil, and both Brazil and the ^Ethiopian region may have been 



