FKAGMENTATION BAlJTtELL 289 



period has come from the Pacific, Arctic, or northern Atlantic realm. 

 At long intervals the geosynclinal seas widen, so that their faunas 

 commingle in the great interior waters and become cosmopolitan. At 

 other times these seas do not coalesce and the faunas remain provin- 

 cial. Therefore during the Paleozoic many of the American faunas 

 derived from northwestern Europe are distinct from those of south- 

 ern Europe, certain faunas from the Maritime Provinces of Canada 

 are easily distinguishable from their contemporaries in the interior 

 Appalachian region. Nevertheless there were times, as in the Middle 

 Cambrian, when the eastern Canadian faunas w^ere closely identical 

 Avith those of northwestern Europe, although both Avere quite distinct 

 from the faunas of southern Europe and the interior of the United 

 States. Contemporary faunas from the latter area correlate best 

 with those of China, both regions belonging to the Pacific realm. 

 Such peculiar relations during times distinguished by an absence of 

 marked climatic zones have led paleontologists to hold that in tlie 

 Paleozoic a land mass extended unbroken across the North Atlantic 

 Ocean, enabling the shallow-Avater faunas to migrate along the 

 northern and southern shelf seas. This inferred northern continent 

 included parts of Canada, Greenland, Iceland, Scandinavia, and 

 Britain in one land which has been named Eria. 



Turning to the evidence supplied by the land life, it is to be 

 noted that in the Pennsylvanian period tlie plants of the great coal 

 swamps Avere largely identical in eastern America and Avestern 

 Europe. The most striking relationships are shown by the flora of 

 the Southern Hemisphere in the early part of the Permian period. 

 At that time the Southern Hemisphere Avas subject to recurrent 

 glaciation on the vastest scale knoAvn in earth history. Continental 

 ice sheets existed in tropic India, southern Africa, and South Amer- 

 ica, Australia, and Antarctica. A special stress flora arose in the 

 Southern Hemisphere adapted to these severe climatic conditions, 

 and the whole assemblage is known as the Glossopteris or Ganga- 

 mopteris flora. This flora has been recovered from all these and 

 other southern lands and is held to haA^e originated here, as it is not 

 represented at this time in the Northern Hemisphere. The spores 

 of these plants could not have crossed thousands of miles of ocean 

 water, and it is equally incredible that a nearly identical assemblage 

 of species could haA^e arisen independently in separated continents. 

 These and similar facts have led many geologists of Europe and 

 America to a belief in the great Paleozoic continent of Gondwana, 

 stretching east and Avest through the Southern Hemisphere and unit- 

 ing South America, Africa, India, and Australia. In the west, 

 Gondwana was separated from Eria by the ancient Mediterranean, 

 which Suess named Tethys, and by the North Atlantic Basin, which 

 Schuchert calls Poseidon. 



