124 NEW YORK STATE MUSEUM 



It may in time become desirable to distinguish the continental 

 masses in their changing outlines in the different periods by separate 

 names. Clarke has, in recognition of the Confusion possible 

 from retaining one name for a changing continental mass, proposed 

 the name " Falklandia " for the Devonian representative of 

 Gondwanaland, because it was connected with Antarctica. We do 

 not know whether the Precambrian ancestor of Falklandia and 

 Gondwana was in any way connected with Antarctica and therefore 

 can not properly use the name Falklandia for the still earlier develop- 

 ment of the continent. It may be suggested that such stages could 

 be distinguished by prefixing the name of the period to the con- 

 tinuous land mass, as Siluro-America and Cambro- Eurasia, retaining 

 the names Eurasia, America and Gondwana for the three arch- 

 continental masses, here described. 



Relation of Precambrian and Paleozoic Continents to Present 

 Mobile Tracts of the Earth 



We have seen in the preceding chapter that the latitudinal extension 

 of the Precambrian continents was preserved with remarkable 

 persistence through Paleozoic time. The series of charts given in 

 text figure 3 show at a glance this persistent character of the large 

 primeval continental masses. The last chart, of late Triassic time, 

 still clearly brings out the same original latitudinal direction of the 

 continents. In the Jurassic period, however, the Indian ocean became 

 definitely established by the foundering of a large portion of eastern 

 Gondwana ; and in Tertiary time the Atlantic ocean finally extended 

 southward between Africa and South America and connected with 

 the Antarctic ocean. As a result of these fracturings of the old 

 continental masses the continents of the present day with their 

 predominating longitudinal extension were formed. 



It would then seem that the Precambrian continental outlines 

 are lost in the present configuration of the surface of the earth. 

 Nevertheless there is good evidence that the old boundary lines 

 of the original Precambrian continents continue to exist as distinct 

 features in the framework of the earth. 



A comparison of figure 4 which represents the original " central 

 massives " or nuclei and also the present mobile or earthquake 

 tracts (together with the tracts of Tertiary folding), with the charts 

 of the Precambrian and Paleozoic continents given before, brings 

 out readily the fact that these mobile tracts, in a most remarkable 

 manner, pass along the supposed boundaries between the Precambrian 



