24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I49 



The percentage limits placed on the zones reflects the pattern which is 

 repeated in the traverses. The limits are, of course, artificial, and 

 in reality the transition from one zone to another is not sharp but 

 gradational. Examination of table 3 indicates that if the percentages 

 from any particular set of seasonal stations in traverse 3 is used, the 

 exact location of a zone's boundary may vary. For instance in June 

 of 1961 the boundary for the E. clavatum zone lies about 3 nautical 

 miles off the Connecticut shore, whereas in November of 1962 the 

 boundary lies 2 nautical miles off the Connecticut shore. Similarly, 

 the exact limits of the B. frigida and E. advena zones also fluctuate. 

 The pattern, however, is always repeated. Figure 10 shows the zona- 

 tion of the living population in L.I.S. The percentages used for 

 traverse 3 are from the grand stations. 



Elphidium clavatum zone. — The percent of E. clavatum increases 

 shoreward, and some of the stations less than a mile from shore are 

 almost entirely composed of this species. E. clavatum is by far the 

 most abundant species in this zone. The upper limit of B. frigida 

 is fixed by definition at 8 percent. E. advena either occurs with very 

 low frequencies or is absent altogether. Elphidium pauciloculum, E. 

 varium, and Reophax dentaliniformis are commonly present, but 

 usually make up less than 15 percent of the living population. The 

 mean depth of stations in this zone is 12 m. and the range 3-23 m. 



Buccella frigida zone. — This zone marks a transition between the 

 E. clavatum and E. advena zones. At many of the stations in this 

 zone E. clavatum and/or E. advena are more abundant than B. 

 frigida. However, B. frigida is usually relatively more abundant in 

 its zone than elsewhere. Elphidium pauciloculum, E. varium, Fis- 

 surina laevigata, and Reophax dentaliniformis commonly occur, but 

 usually do not make up more than 15 percent of the living population. 

 The mean depth of stations in this zone is 25 m. and the range 

 15-33 m. 



Eggerella advena zone. — In this zone the living population is domi- 

 nated by E. advena. Occasionally E. clavatum or B. frigida may be 

 relatively more abundant than E. advena, but usually the reverse is 

 true. Elphidium pauciloculum, E. varium, Fissurina laevigata, and 

 Reophax dentaliniformis occur, but usually make up no more than 20 

 percent of the living population. The mean depth of stations in this 

 zone is 29 m. and the range 16-39 m. 



Comparison of the Number of Living Individuals in Traverses 2 and 3 



Traverse 2 was sampled on November 19, 1962, and one of the 

 sampling times of traverse 3 was on November 20, 1962. Owing 



