50 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I49 



three abundant species. The L/T frequency distribution of E. clava- 

 tum has values of less than 20 percent at all stations except 6 and 10. 

 The high at station 6 is due to a slight increase in the living population 

 of E. clavatum combined with a slight decrease in the dead population. 

 At station 10 both the living and dead populations are increasing, 

 but the living population is increasing at a greater rate. The L/T 

 ratio of B. frigida is less than 20 percent at all stations except 9, 10, 

 and 11. The maximum is the result of an increase in the living 

 population combined with a decrease in the dead population at these 

 stations. The L/T ratio of E. advena is greater than 70 percent at 

 all stations except 8, 9, 10, and 11. At stations 8 and 9 the dead 

 population increases whereas the living population remains constant, 

 resulting in lower L/T values. At stations 10 and 11 both the living 

 and dead populations are decreasing, but the living population 

 decreases more rapidly. 



The L/T frequency distribution of all species indicates that at 

 stations 3 to 8 the distribution is controlled by the L/T ratio of E. 

 advena, the most abundant species in this area. At station 9, the 

 L/T ratio of B. frigida becomes important, while at stations 10 and 11 

 the L/T ratios of B. frigida and E. clavatum control the distribution. 

 Stations 12 and 13 are in an area where E. clavatum is most abundant 

 and its L/T ratio controls the distribution of these stations. Station 

 2 also has a low L/T value for all species owing to the influence of 

 E. clavatum. 



If the L/T ratio of all species is an accurate indicator of the 

 relative rate of sedimentation, then the L/T ratios of the component 

 species should show the same pattern. In traverse 3, the L/T ratios 

 of the three abundant species each give a different interpretation of 

 the relative rate of sedimentation. The L/T ratio for E. advena is 

 always high, and it is likely that empty tests of this fragile arenaceous 

 species are being destroyed. 



Figure 22 shows the L/T ratios expressed in percent for the sta- 

 tions in L.I.S. The values for traverse 3 are seasonal averages. 

 In general, the ratios are higher in the central area (£. advena zone) . 



SIGNIFICANCE OF ENVIRONMENTAL FACTORS 



I have shown that the number of foramini feral species increases to 

 the east and that the number of living Foraminifera in the Eggerella 

 advena zone of traverse 2 (west) is greater than in traverse 3 (cen- 

 tral). It was also observed that the most striking change in the 

 foraminiferal fauna is with depth. Broadly speaking, the fauna can 



