VII.] SPECIES AXD SPACE. 161 



Thus the genera Clarias 7 Heterobranchus 8 are found 

 both in Africa and the East Indies. Plotosm is found in 

 Africa, India, and Australia, and the species P. anguillaris ' 

 has been brought from both China and Moreton Bay. 

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

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

 t'lough entering rivers, yet lives in the sea. 



Ewtropim 10 is an African genus, but E. .obtusirostris 

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

 American form ; but one species, A. Cantonensis" comes- 

 from China. 



The genus G-alaxias ia has at least one species common 

 to New Zealand and South America, and one common to 

 South America and Tasmania. In this genus jve thus have 

 an absolutely and completely fresh-water form of the very 

 same species distributed between different and distinct geo- 

 graphical regions. 



Of the lower fishes, a lamprey, Mordacia mordax is 

 common to South Australia and Chili ; while another form 

 of the same family, namely, G-eotria Chilensis 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 



7 See Catalogue, vol. iii., p. 13. Ibid., p. 21. 



9 Ibid., vol. v., p. 24. Ibid., p. 52. Ibid., p. 100. 



19 Ibid., voL vi., 208. 13 Ibid., vol. viii., p. 507. 14 Ibid., p. 509. 



