. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Mesopelagic Atlantic Fishes • Backus cf al. 153 1000. O — c\j o o o 00 00 CD CD O — CVJ to OD CO 00 00 00 COLLECTION NUMBER Fig. 8. Numbers of species and specimens per collection for each of Collections 800-813. tial Water and North Atlantic Central Water Masses. A good working rule would seem to be that when the 200-meter temperature in these latitudes is in excess of about 15" C, the observer is in the North Adantic Central Water Mass; when the 200-meter tempera- ture is less than about 13'C, the observer is i
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Mesopelagic Atlantic Fishes • Backus cf al. 153 1000. O — c\j o o o 00 00 CD CD O — CVJ to OD CO 00 00 00 COLLECTION NUMBER Fig. 8. Numbers of species and specimens per collection for each of Collections 800-813. tial Water and North Atlantic Central Water Masses. A good working rule would seem to be that when the 200-meter temperature in these latitudes is in excess of about 15" C, the observer is in the North Adantic Central Water Mass; when the 200-meter tempera- ture is less than about 13'C, the observer is in the South Atlantic Central Water Mass. Isotherms for these temperatures at the 200- meter level are given by Schroeder (1963) and her plate 4 should be of great use to zoogeographers working in this area. Although the boundary noted marks the meeting of the North and South Atlantic Central Water Masses, it is not, in terms of circulation, the meeting of the central gyres of these two oceans. These gyres are separated by an equatorial zone defined by the shallow thermocline of steep gradient already noted ("the well-known equatorial discontinuity layer," Voorhis, 1961). The degradation of this layer can be said to mark the poleward limits of the eciuatorial zone. To the north, the boundary of this zone and the boundary between North and South Atlantic Central Water Masses are thus co-determined. Does this boundary have faunal significance because it marks the northern edge of the equatorial zone or because it marks the meeting of North and South Atlantic Central Water Masses? For the time being we must beg the ques- tion. It can be approached by determining, when collections are available, the faunal. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Harvard University. Museum of Comparative Z
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