182 POPULATIONS OF THE SEA 



analogies between the Devonian couple and the Recent North 

 Atlantic faunas, which involve distances and potential intermediate 

 stepping stones of about the same order of magnitude. Although 

 such a comparison is hindered by the fact that mainly subtropical 

 west Atlantic species are compared with temperate east Atlantic 

 species (Fig. 9A), it is nevertheless impressive to find an 11% 

 transoceanic nomenclatural identity between faunas of about 1600 

 species from different latitudinal zones. The same check list (Dall, 

 1889), incidentally, shows 6 out of 21 morphological species and 

 varieties of living brachiopods native to the southeastern United 

 States as occurring in Europe : a 29% identity that compares more 

 favorably with that between members of the Devonian couple 

 (Fig. 9B, C), 



If, as it seems, similarities in the Early Devonian faunas of the 

 southern hemisphere are not a compelling argument for former 

 continental connection, how else may they be explained? These 

 similarities could be explained without catastrophic geographic 

 changes if eastward and northeastward flowing currents such as 

 now encircle Antarctica as the great West Wind Drift (Fig. 5) 

 existed in Devonian time and dispersed floating larvae from a 

 circum-Antarctic shelf-sea to the shores of southern hemisphere 

 land masses having similar marine faunas, and provided that such 

 dispersal were repeated at frequent enough intervals to retard 

 local endemism. That Devonian Antarctica was ice-free is implied 

 by the presence of Late Devonian fish well up in the thick and 

 apparently uninterrupted later Paleozoic terrestrial deposits of 

 eastern Antarctica (Adie, 1952), and by the occurrence in the 

 American sector of Early Devonian brachiopods which came 

 to my attention through the courtesy of W. E. Long. The 

 probable intermittent presence of isthmian linkage between 

 Antarctica and other southern hemisphere lands (e.g., Axelrod, 

 1960, Figs. 6, 8, and 9) provides a contributary or alternative 

 explanation, but probably it is not necessary to explain the 

 paleobiogeographical facts. 



The answer may be found in more and larger collections of 

 Antarctic and other southern hemisphere fossils, which should be 

 a primary objective of "Post-Geophysical Year" investigations. 



