ID "TERRA NOVA EXPEDITION. 



Our knowledge of the distributi f the pelagic anil deep sea fishes of the 



Antarctic Ocean is obviously not sufficiently complete to permil of an attempt to 

 co-ordinate the results so far obtained. 



2. THE ANTARCTIC CONTINENT DURING THE 

 TERTIARY PERIOD. 



Manv authorities believe that in the early Tertiary the Antarctic continent 

 was connected with Australia and with South America ; some think with Africa 

 also. The distribution of the Fishes, ami of other groups of animals, has been 

 considered to support this hypothesis. 



Fishes. 



Tin' distinctive features of the fish-fauna of the coasts of Antarctica are that 

 nearly all the genera and species are peculiar and that they nearly all belong to a 

 single group, the Nototheniiformes, which is characteristic of and almost restricted 

 to the Antarctic and Subantarctic Zones. In the Antarctic Zone this group has 

 developed into a large number of types that differ greatly in structure, appearance 

 and habits. These facts seem to point to the conclusions that Antarctica may have 

 long been isolated and that its coasts may have been washed by a cold sea for a 

 long time, probably throughout the Tertiary Period. 



It has been suggested that identical or related species of different parts of the 

 South Temperate Zone are part of the fauna of the coasts of an Antarctic continent 

 that formerly connected America. Africa and Australia. It is very difficult to make 

 this view harmonise with the facts. Tristan da Cunha and St. Paid. 4,500 miles 

 apart, have at least two species of shore fishes (Ldhrichtki/N ornatufi and Chilodactylus 

 maiiodactylus) in common. Have these persisted unchanged whilst the coasts of 

 Antarctica have receded to their present position, ami whilst tin' fauna of Kerguelen 

 has become differentiated? It seems far more likely that the distribution of these 

 species is due to present conditions; Tristan da Cunha ami St. Paul are nearly in 

 the same latitude and on the same isotherm, and the Antarctic Drift runs directly 

 from one to the other. In all probability it will be found that the species common 

 to both islands have Boating eggs and larvae that swim at the surface: it is even 

 possible that the adult fish may occasionally migrate from one island to the other. 

 The case of related species, as for example Scriolella velaini from St. Paul, and 

 S. aiitarcfifti from Tristan da Cunha, may be explained on similar lines: it is 

 evident that the distance between the islands is too greal to be traversed by these 

 species, 1ml under somewhal different conditions the parent form may have lived 

 at both and either at the Cape or at Marion and the Crozets, or at other islands 

 that may have existed and served as stepping stones, but have now disappeared. 

 Whatever ma\ lie the true explanation, it is certain that the construction of 



