IGG 



THE GENESIS OF SPECIES 



[Chap. 



connexion between Africa and India, liannonizing with 

 what we learn from jMiocene nianimalian remains. 



On the uther hand, the Cliaracinida3 (a family of the 

 physostomons tislies) are found in Africa and South Ame- 

 rica, and not in India; and even the com])onent groups of 

 the fiimily are so distributed, — namely, the Tdragono})- 

 tcrina^ and the Hyd rocyoninar 



Again, we have similar phenomena in that ahnost ex- 

 clusively fresh-water group the Siluroids. 



Thus the genera Clarias^ and Jfctcrohrmchus'^ are found 

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

 Africa, India, and Australia, and the species P. aiujLiillaris'^ 

 has been brought from both China and IMoreton Bay. 

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

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

 though entering rivers, yet lives in the sea. 



EiUropius^ is an African genus, but E. obtusirostris 

 comes from India. On the otli^x \\ix\id, Amiur us is a Xorth 

 American form ; but one species, A. cantonensis^ comes 

 from China. 



The genus Galaxias^ has at least one species common 

 to New Zealand and South America, and one common to 

 South America and Tasmania. In this genus we thus have 

 an absolutely and completely fresh-water form of the rrv)/ 

 same species distributed between different and distinct 

 geographical regions. 



Of the lower fishes, a lamprey, Mordacia mordax,^ is 

 common to South Australia and Chile ; while another form 



I See Catalogue, vol. v. p. 311. 



•■« Ihi.l. p. 13. •» Ibid. p. 21. 



« Ibid. p. 52. " Ibid. p. 100. 



" Ibid. vol. viii. p. 507. 



2 Il)id. p. 345. 



* Ibi.l. p. 24. 



8 Ibid. vol. vi. p. 208. 



