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University of California. 



[Vol. i. 



tion of the American continent from 3,000 to 5,000 feet, and its 

 extension to the border of the now submerged continental margin, 

 and the formation of mountain ranges of monoclinal type; besides 

 the broad connection with Asia by the Behring region, and with 

 South America by the Antillean region; besides the enormous cli- 

 matic changes and its resulting ice sheet, we must add also great 

 extensions of lakes so as to form inland fresh water seas in the 

 Canadian Lake region and in the Basin region. We must add also 

 the greatly increased elevation of the plateau region and the cutting 

 of the inner gorge of the Grand Canon, and the cutting of all the 

 grand gorges which trench the flanks of the Sierra Nevada. 



Equally great epeirogenic movements are known to have 

 occurred in Europe, Africa, and South America, but it would carry 

 us too far to dwell on these. 



Psychozoic Era. — I repeat, then, that the present must be re- 

 garded as a primary division of time, i. e., an Era. If so, it deserves 

 a distinctive name as such. I have called it the Psychozoic Era. 

 If anyone can suggest a better name, I shall willingly adopt it. 



I have treated the Quaternary or glacial period as a transition 

 or critical period between two great eras, the Cenozoic and the Psy- 

 chozoic. To which of these it ought to be united is a question of 

 less importance. Critical periods are usually largely lost intervals. 

 This one, partly because the oscillations were perhaps not so great, 

 but mainly because it is so recent, has been recovered. The lost 

 records of other critical periods have also been partly recovered, 

 and more will be recovered hereafter. In these former critical peri- 

 ods the recovered record has usually been united with the previous 

 era. The new era commences only when the new forms are well 

 established. Thus the Permian is united with the Palaeozoic and 

 the Laramie with the Cretaceous. Therefore it is proper that the 

 Quaternary or glacial period should be united with the Cenozoic. 

 But unfortunately it has been usually supposed that this carries with 

 it also the Present as a mere epoch of the Quaternary. Because 

 the record of this interval has been entirely recovered ; because the 

 change in this case is seen to be gradual instead of apparently sud- 

 den, as is often the case in other critical periods; and finally because 

 it is not yet completed but still going on under our eyes, most geol- 



