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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 149 



■5 



c m 



o 



V 



2 



c 2 



20- 



10 - 



10 20 30 40 

 Depth in m. 



C W 



o 



Z 



10 20 30 40 

 Depth in m. 



.E => 200 



2 e 



E S 



O LJ 



10 20 30 40 

 Depth in m. 



Fig. 8. — Distribution of abundant species with depth. 



The exact limits of the zonation were chosen empirically through 

 careful examination of table 3 (page 72). The following zones are 

 recognized : 



Elphidiutn clavatum zone : 



E. clavatum ^60% 



B. frigida < 9% 



Buccella frigida zone: 

 B. frigida ^ 9% 

 E. advena < 19% 



Eggerella advena zone : 

 E. advena ^ 19% 



