302 THE TRANSFORMATIONS OF THE ANIMAL WORLD 



It really seems to result from the facts collected 

 above that migrations must have taken place from 

 Europe to America at three different periods of 

 Secondary times : first in the Trias, next in the 

 upper Jurassic, and lastly in the middle Cretacean 

 age. In any case, no other explanation can be 

 imagined for the interchanges of faunas, such as the 

 passage from Europe to America of the Megalo- 

 sauridse, the Sauropods, the Pterosaurians, the 

 Pleuroderous Turtles, and for the probably converse 

 migration of the Cseluridse, the Stegosaurians, and 

 the Ceratopsidae. 



Like the Boreal Continent, the great Continent of 

 the Austral Hemisphere, or Continent of Gondwana, 

 extending from Australia to South America, com- 

 menced to break up during the Secondary era. At 

 an early date, starting from the Liassic epoch, a 

 zone of marine subsidence, in a north to south 

 direction, separated this great tract into two distinct 

 fragments : on the east, the Australian-Indo- Mada- 

 gascar Continent, comprising Australia, the Indian 

 Peninsula, the site of the present Indian Ocean, and 

 Madagascar ; on the west, beyond the slightly en- 

 larged Mozambique, the Africano - Brazilian Con- 

 tinent, composed of the greater part of Africa and 

 South America joined across the South Atlantic. 



This Secondary palaeogeography, founded on the 

 distribution of marine deposits, is confirmed and 

 made clear by the migrations of terrestrial animals. 

 At the Triassic epoch, the Continent of Gondwana 

 probably still existed in its entirety. Amphibians 

 of several groups possess in fact representative 

 forms similar enough, in Australia and India, on 



