THE OPALINID CILIATE IXFUSORIANS. 



305 



authors emphasize to different degrees the several lines of evidence, 

 from sedimentary rocks, from fossils, and from the present distribu- 

 tion of animals and plants. 



There is among paleogeographers rather general agreement that 

 there have been, since the middle Carboniferous period, three chief 

 land masses : i, An Antarctic continent, Antarctica, connected part 

 of the time with Australia, New Zealand, and Patagonia, and not 



