OCEANS AND THEIR HISTORY 15 



reconstruction have been made, one of the most recent 

 being propounded by the Austrahan geologist Fair- 

 bridge."^ In late Paleozoic time a large part of what is 

 now the bottom of the Indian Ocean is assumed to have 

 been above sea level: the famous Gondwana Land, 

 which united Australia and the Antarctic with south- 

 eastern Asia. Lemuria, a last remnant of this ancient 

 continent, hypothetic ally linked East Africa and Mada- 

 gascar with the Indian Peninsula. Because of a break in 

 the earlier parallelism existing between the paleonto- 

 logical series found on the two continents, the Lemurian 

 land bridge is assumed to have foundered in Mid- 

 Tertiary time. According to Fairbridge the Indian 

 Ocean in its present shape is the youngest of the three 

 oceans. Its northwestern part he assumes to have been 

 formed "only" 10 to 20 million years before our time. 



However, it is our own ocean, the Atlantic, which has 

 given rise to the most fantastic attempts at reconstruc- 

 tion. Here the paleontologists insist there were three 

 transverse land bridges, separated by the two arms of the 

 ancient sea of Thetys, as shown by Figure 7.^ Far to the 

 north the Archiboreis linked northern Europe and the 

 Arctic islands with North America. Farther south, 

 Archatlantis ran across the present Atlantic Ocean from 

 the West Indies to northern Africa. Finally, Archhelenis 

 spanned the southern Atlantic Ocean from Brazil to 

 South Africa. 



Much fiercer than the discussion over land bridges 

 was that provoked by the famous theory of "continental 



