CHAPTER XII 



SUMMARY OF THE LIFE OF THE PLEISTOCENE WITHIN THE 

 ENGLACIATED PORTION OF NORTH AMERICA 



In the tables at the end of this chapter the biota of the Pleistocene, in that 

 part of North America covered at one time or another by a drift sheet, is 

 arranged to show both systematic and stratigraphic sequence, upward of 685 

 species of animals and plants being listed. A study of the table below, which 

 is a summary of the large tables at the end of this chapter, brings out some 

 striking features. 



Table Showing Number of Living and Extinct Species Recorded from the 

 Glaciated Portion of North America 





Living 



Extinct 



Total 



Percent 

 extinct 



Plants 



138 



292 



4 



4 



37 



7 



6 







104 



93 



145 



298 



4 



108 



130 



4.8 



Animals 



Mollusca 



2. 



Crustacea 







Insecta 



96.3 



Vertebra ta 



71.5 







Totals 



475 



210 



685 



30.7 







The plants and mollusks are seen to have suffered but little change thru- 

 out the Glacial Period, the percentage of extinct species being about 4.8 per 

 cent in plants and 2 per cent in mollusks. Among the insects and verte- 

 brates, however, the case is reversed; of the former, about 96.3 per cent are 

 extinct, and of the latter about 71.5 per cent are extinct. The percentage of 

 extinct mammals varies considerably, decreasing with the advance in time of 

 the Glacial Period. Thus the Port Kennedy cave fauna, herein considered as 

 preglacial, contains 80 per cent of extinct species, while the Conrad Fissure 

 fauna, placed by Hay in the Sangamon interglacial interval, 1 contains 47 per 



'Dr. Hay places this fauna in the Sangamon (Smith. Mis. Coll., LIX, pages 14-15; 

 Iowa Geol. Surv., XXIII, pages 31-32) but as it is believed to have been destoyed by the 

 influence of the Illinoian ice invasion, its true age must be the interval preceding this invasion, 

 or the Yarmouth (See Science, XXX, page 892, 1909). 



