. -2S 2LXX so^E-iyo^E aOO TOO 600 100 400 HOUTM 300 200 too .[f- 100 iOO JOG â ! 'Ale NAUTICAL MILES 00 SOO boo 700 800 SOUTH Fig. 5. The distribution of adolescent and adult E. triacantha in relation to the Antarctic convergence in the Greenwich meridian compared with that in the sector 90° £-170° E (see Fig. 4 for explanation). It will be seen that the total north-south range is considerably greater between 90° E and 170° E than on the 0° line; it extends over 1350 miles in the former and only 700 miles in the latter. The range over which E. triacantha is abundant is, however, similar
. -2S 2LXX so^E-iyo^E aOO TOO 600 100 400 HOUTM 300 200 too .[f- 100 iOO JOG â ! 'Ale NAUTICAL MILES 00 SOO boo 700 800 SOUTH Fig. 5. The distribution of adolescent and adult E. triacantha in relation to the Antarctic convergence in the Greenwich meridian compared with that in the sector 90° £-170° E (see Fig. 4 for explanation). It will be seen that the total north-south range is considerably greater between 90° E and 170° E than on the 0° line; it extends over 1350 miles in the former and only 700 miles in the latter. The range over which E. triacantha is abundant is, however, similar in both regions, though in the Green- wich meridian the northern and southern limits are some 150-200 miles further north. There is little doubt that the southward spread of E. triacantha in the South Atlantic (0°) is re- stricted, at least to some extent, by the Weddell drift, the core of which crosses the Greenwich meridian in about 60° S (Deacon, 1937, p. 28). The northern limit of the Weddell drift is not clearly defined, but Deacon (p. 25) records two occasions in the mid-South Atlantic when a marked temperature change has indicated a convergence between Antarctic water coming from the north of Graham Land through Drake Passage and that from the Weddell Sea. One occurred in approximately 55° S, 22° W and the other, less clearly marked, between 51° 20' S, 07° E and 52° S, 06° E. The boundary, being further south to the west of these last two positions, is likely, in 0°, to occur between 53° S and 54° S. This corresponds to a position some 130-250 miles south of the mean position of the Antarctic convergence in 0° and it will be seen from Fig. 5 that the number of E. triacantha fall off considerably in this region. Ommaney (1936, p. 297) found a similar distribution in Rhincalanus gigas Brady, 1883, that is a falling off in numbers to a level of comparative scarcity in the Weddell Sea water. In the Indian Ocean (Fig. 5, 90°
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