48 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I49 



Similarly, the distribution of species cannot be related to particle 

 size of the sediment. For example, at station 12 the sediment is a 

 clayey silt consisting of 11 percent sand, 58 percent silt, and 31 per- 

 cent clay ; the number of living Elphidium clavatum is 600, Buccella 

 frigida 53, and Eggerella advena 0. At station 8 the sediment is a 

 clayey silt consisting of 14 percent sand, 55 percent silt, and 30 per- 

 cent clay ; the number of living E. clavatum is 0, B. frigida 23, and 

 E. advena 106. Examination of the data indicates numerous exam- 

 ples of faunal change without any relation to the particle size of the 

 sediment. 



The lack of Foraminifera in traverse 5 is puzzling. Stations 54 

 and 58 contain less than 2 percent silt and clay, but stations 55 and 

 57 contain over 50 percent while station 56 contains 8 percent. 

 Clearly, the absence of living Foraminifera (stations 54 and 55 con- 

 tain one individual each) at all these stations cannot be attributed to 

 an insufficient amount of silt and clay. 



Ratios of Living to Total Populations in L.I.S. 



Phleger (1951) discussed and used the living and total populations 

 of Foraminifera in estimating relative rates of sedimentation in the 

 Gulf of Mexico. Walton (1955) used the ratio of living to dead 

 populations to indicate relative rates of sedimentation in Todos Santos 

 Bay. Phleger (1955) expressed the ratio of living to total popula- 

 tions (L/T) in percent and estimated relative rates of sedimenta- 

 tion in the southeastern Mississippi delta area. The use of an L/T 

 ratio is based on several assumptions which have been discussed in the 

 papers mentioned above. If the living population represents the rate 

 of addition of tests to the sediment and the total population represents 

 this accumulation over a period of time, then the ratio L/T indicates 

 the relative rate of sedimentation providing tests are not removed 

 from the sediment. If sedimentation is rapid, the L/T ratio will be 

 high because empty tests are being rapidly buried. 



The frequency distribution for the L/T ratio expressed in percent 

 is shown in figure 21 for all species, Elphidium clavatum, Buccella 

 frigida, and Eggerella advena, in the 13 grand stations of traverse 3. 

 The frequency distribution of the L/T ratio of all species has maxi- 

 mum values in the central area of the traverse and minimum values 

 at the ends. It would appear, then, that sedimentation is relatively 

 more rapid in the central areas than near shore. 



Let us examine the L/T frequency distribution of all species in 

 greater detail by examining the L/T frequency distributions of the 



