TEISTAN DA CUNHA 393 



St. Helena, Ascension island, the Cape Verd islands, the 

 Canaries and Madeira, is a matter which must be left to future 

 observations. Certain faunistic features appear to be in 

 favour of such a theory. 



Tristan da Cunha is almost as large as St. Helena. It 

 lies considerably further south, being bleak and inhospitable 

 in the extreme, owing to its proximity to the northern boun- 

 dary of the antarctic ice-drift. The flora is quite different 

 from that of St. Helena, as it possesses antarctic affinities. 

 The genera Nertera, Uncinia and Acaena inhabiting antarctic 

 America, New Zealand or Australia occur here also. It has 

 Lomaria alpina, in common with South America, Kerguelen 

 island, New Zealand and Australia, while Spartina arundi- 

 nacia occurs in Tristan da Cunha and St. Paul, and is related 

 to a South American species.* The most remarkable member 

 of the fauna is the genus Tristania which, with its two species, 

 is confined to the island. It is related to the snail Opeas which 

 inhabits both Africa and South America. 



Almost three hundred miles further south there is still an- 

 other volcanic island, of which scarcely anything was known 

 until it was visited by Dr. Bruce, the leader of the Scottish 

 National Antarctic Expedition. First called "Diego 

 Alvarez " according to Dr. Brown,f its name was later on 

 changed to " Gough island." The island differs from some 

 of the other islands referred to, in being densely covered with 

 vegetation, which is similar in character to that of Tristan 

 da Cunha. While showing the same general affinities, Diego 

 Alvarez seems to have a stronger American element than the 

 islands forming the Tristan da Cunha group. The land birds 

 comprising two species of bunting (Nesospiza) and a galli- 

 nulo (Porphyriornis) are peculiar to the island, but related 

 to species living on Tristan da Cunha. 



To briefly review the results of our studies so far, it appears 

 highly probable that Brazil was entirely separated from 

 western South America in Mesozoic and part of Tertiary 

 times, but was connected with the highland of Guiana across 

 the mouth of what is now the Amazon river, which flowed 



* Engler, A., " Entwicklungsgeschichte der Florengebiete," II., p. 159. 

 t Brown, K. N. E., " Diego Alvarez," pp. 9 10. 



