370 POLAR PROBLEMS 



northern boundaries of the Antarctic and sub-Antarctic zones. Regan 

 further divides the fauna into coastal and oceanic assemblages, in- 

 cluding in the former not only the littoral fishes but also those which 

 occur not far from the coast, in waters down to a depth of 300 fathoms, 

 and which are not pelagic or bathypelagic. 



The Antarctic zone includes therefore the coasts of the polar 

 continent and all islands which lie to the southward of the isotherm 

 of 6° C, "with the probable exception of Macquarie." In this zone 

 we find an absence of south temperate types, a high percentage of 

 peculiar genera, and few species which range beyond the limits of 

 the zone. In the division which Regan terms the Glacial district, 

 90 per cent of the fishes are Nototheniiformes, a Percoid group con- 

 fined to waters of the far south and somewhat analogous to the cod 

 group of the northern hemisphere, although in appearance many of 

 them rather resemble sculpins. Most of the other fishes of the Glacial 

 district are eelpouts (Zoarcidae), many of the species of which are 

 circumpolar. The Zoarcidae also have sub-Antarctic representatives, 

 of which Lycenchelys and Melanostigma represent northern deep-water 

 genera which have no species in the south temperate zone. 



The Kerguelen, or peri-Glacial district, which includes the Crozet 

 Islands and others lying south of the limit of pack ice, is a small and 

 somewhat impoverished branch of the Antarctic zone, but with well- 

 marked characters of its own. 



The sub- Antarctic zone, covering generally the regions between 

 the surface isotherms of 6° and 12° C., is penetrated by a number 

 of south temperate types. Galaxiidae are characteristic; most of 

 the Nototheniiformes belong to the genus Notothenia, and there 

 are several peculiar Zoarcidae, 



The Nototheniiformes as a group extend northward to the conti- 

 nents of South America, Africa, and Australia, to New Zealand, 

 Juan Fernandez, Tristan da Cunha, St. Paul, and Amsterdam. They 

 are divided into four distinct families and their present variety indi- 

 cates, according to Regan, the existence of a large cold southern 

 ocean throughout a great period of time. Bovichthys is the most 

 northerly genus, and Trematomus the most southerly. It is interesting 

 and true to form to note that no Bovichthys is of circumpolar distribu- 

 tion, a distinct species being found in each of the sub-Antarctic areas. 

 In Trematomus, on the other hand, most of the known species are 

 circumpolar. The condition harmonizes, incidentally, with what is 

 known of the circumpolar distribution of fishes in the Arctic. 



ZOOGEOGRAPHIC RELATIONSHIPS OF THE MaMMALS AND BiRDS 



So far as the orders and families of birds and mammals are con- 

 cerned, the Antarctic by no means forms a distinct province. Among 



