VII.] SPECIES AND SPACE. 161 



Thus the genera Clarias'' Ileterohranchits* vltg found 

 both in Africa and tlie East Indies. Plotosus is found in 

 Africa, India, and Australia, and tlie species P. anguillarU* 

 lias been brought from both China and Morcton Bay. 

 Here, tlierefore, we have the same species in two distinct 

 geographical regions. It is, however, a coast fish, which, 

 though entering rivers, 3'et lives in the sea. 



Eatropius '" is an African genus, but E. ohtusirostris 

 comes from India. On the other hand, Amhtrits is a North 

 American form; but one species, A. Canto)iensis" comes 

 from Cliina. 



The genus Gfalaxias " has at least one species common 

 to New Zealand and South America, and one conunon to 

 South America and Tasmania. In tliis genus we thus have 

 an absolute!}' and completely fresh-water form of the very 

 same species distributed between different and distinct geo- 

 graphical regions. 



Of the lower fishes, a lamprey, 3fordacia mordax^^* is 

 common to South Australia and Chili ; while another form 

 of the same family, namely, Geotria Ghiletisis,^* is found 

 not only in South America and Australia, but in New Zea- 

 land also. These fishes, however, probably pass part of 

 their lives in the sea. 



We thus certainly have several species which are com- 

 mon to the fresh waters of distant continents, although it 

 cannot be certainly affirmed that they are exclusively and 

 entirely fresh-water fishes throughout all their lives except 

 in the case of Galaxias. 



Existing forms point to a close union between South 

 America and Africa on the one hand, and between South 

 America, Australia, Tasmania, and New Zealand, on the 

 other ; but these unions were not synchronous any more 



' See Catalogue, vol. ill., p. 13. " Ibid., p. 21. 



• Ibid., vol. v., p. 24, 'o Ibid., p. 52. " Ibid., p. 100. 



" Ibid., vol. vl., 208. " Ibid., vol. viii., p. 507. '* Ibid., p. 609. 



