174 U.S. NATIONAL MUSEUM BULLETIN 291 



tows shallower than 750 m shows that 7 of the 8 specimens greater than 

 30 mm were taken in one tow and the remaining specimen was taken 

 in an adjacent tow. These two unusual captures (1133 and 1137) were 

 made south of 66 °S in the area of up welling along the Antarctic 

 Divergence. Of the 11 specimens below 30 mm MIj taken in less than 

 750 m 10 are larvae and juveniles 21 mm ML or smaller. Nine of these 

 were taken in two tows in the Peru Current ; the other two came from 

 tows in the convergence zone. Another tow that captured 6 specimens 

 above 30 mm fished at depths that varied from 823-1300 m ; these have 

 been plotted at the shallower depth but could just have easily come 

 from 1300 m; this tov/ (812) also came from a southern locality, 64° 

 45'S, where up welling occurs. One other shallow tow (1383) to 914 m 

 accounts for 10 more of the shallow specimens above 30 mm mantle 

 length; this station was located at 55 °S 149 °W in the tongue of frigid 

 water that extends northeastward from the Ross Sea, possibly an area 

 of strong vertical movement. Therefore, all except 6 specimens larger 

 than 30 mm that were captured in less tlian 1000 m came from a few 

 tows that fished in areas of unusual conditions, particularly upwell- 

 ings. Further, the great majority of tows in less than 1000 m caught 

 only small specimens or mostly small specimens with only one or two 

 larger individuals. 



The calculations in the previous section indicate that B. dbyssicol<i 

 probably does not live below 2500 m. Therefore, the 35 si>ecimens that 

 came from nets that fished at depths greater than 2500 m may have 

 come from the shallower depths, presumably from the zone of abun- 

 dance. 



A method for the proportional redistribution of the deepest living 

 specimens has been devised. The size group above 30 nrni had 23 speci- 

 mens captured deeper than 2500 m. It is assumed that they were dis- 

 tributed in the 2000-2500 m zone in numbers proportional to the 

 plotted distribution; 112 specimens are plotted in the zone: 65% (73) 

 from 2000-2200 m, and 35% (39) from 2200-2500 m. Therefore, about 

 two-thirds (or 15) of the specimens from below 2500 m can be added 

 to the 2000-2200 m zone, bringing the total number of specimens in 

 that zone to 88 and in the overall zone of abundance (1650-2200 m) 

 to 184, a 4% increase. 



Specimens in the less than 30 mm size group are evenly distributed 

 in the 2000-2500 m range; 12 specimens are plotted below 2500 m. 

 (Actually, specimens below 2000 m are relatively sparse and it is 

 possible that that depth is the lower limit of vertical range for small 

 specimens.) It might be tempting to redistribute all the small speci- 

 mens from greater than 2000 m into less than 2000 m, but it is safer 

 for the present to redistribute only those from greater than 2500 m. 



