256 



THE ORIGIN AND EVOLUTION OF LIFE 



the eastern and western hemispheres were connected both at 

 the north pole and at the south pole, or through Arctic and 

 Antarctic land areas, still has many adherents, especially in 



PER I O D S 



GLACIAL kQUATERK ABV 4000 



HIMALAYAS 



SWISS ALPS 

 PYRENEES 



PLIOCENE 5000 



i I ■ Ml I I 

 , PREJACEOUS 



-+^T^ 



I I I 

 TRiA^sic I I I I 



I I I ' I I '13000 



P^RMi , ; , , 



I L j j J I , | i^° 9° i, 



THE HERCYNIAN BELT OF 



CENTRAL EUROPE? ////'// ''^'/ 



// CAJ^BONIFERJlyS- ' 



•/-^/OEWINIAN^/^ 

 ;x//.^/g?OO0 



SCOTTISH HIGHUNDS/ 



FINLAND 



E.SCANDir 



S.BOHEMM 



ORDOVICIAN 



17000 



E. SCANDINAVIA 



CERTAIN MOUNTAIN CHIEF MOUNTAIN 



REVOLUTIONS OF' REVOLUTIONS OF 



EUROPE AND ASIA NORTH AMERICA 



AGE 



OF 

 MAMMALS 



Fig. 121. Main Subdivisions of Geologic Time. 



The subdivisions are not to the same scale. The notches at the sides of the scale (which 

 is simplified from that on p. 153) represent chiefly the periods of mountain uplift in the 

 northern hemisphere of the Old World (left) and of the New World (right). 



regard to the former relations of the Australian continent 

 and South America through the now partly sunken continent 

 of Antarctica. The still more conservative ''north polar 



