232 FISHES. 



of the two regions these fishes first made their appearance, 

 but the discovery of remains of Notopteridm and Silurina 

 in tertiary deposits of Sumatra points to the Indian region 

 as their original home. We can have less doubt about the 

 other fishes common to both regions ; they are clearly immi- 

 grants into Africa from the East, and it is a remarkable fact 

 that these immigrants have penetrated to the most distant 

 limits of Africa in the west as well as in the south, — viz. the 

 Ldbyrinthici, represented by two genera closely allied to the 

 Indian Anabas; the Ophiocephalidce and Mastacemhelidm, a 

 few species of which have penetrated to the west coast, 

 singularly enough being absent from the eastern rivers ; the 

 Ariina, represented by several species, of which one or two 

 are identical with Indian, having extended their range along 

 the intervening coasts to the east coast of Africa. The 

 Cyprinoids also afford an instance of an Indian species 

 ranging into Africa, viz. Discoc/nathus lamta, which seems 

 to have crossed at the southern extremity of the Eed Sea, 

 as it is found in the reservoirs at Aden and the hiU-streams 

 of the opposite coast-region of Abyssinia. 

 - 2. No such direct influx of species and genera has 

 occurred from South America into Africa. Yet the affinity 

 of their Freshwater fishes is striking. Two of the most 

 natural families of fishes, the Ghroviides and Characinidce, are 

 peculiar, and (with the exception of Mroplus) restricted to 

 them. The African and South American Dipnoi are closely 

 allied to each other. The Pimelodina, so characteristic of 

 Tropical America, have three representatives in Africa, viz., 

 Pimelodus platychir, P. halayi, and Auchenoglanis hiscutatus ; 

 the Doradina are another Siluroid group restricted to these 

 two continents.^ Yet, with all these points of close resem- 



' "We have left out from these considerations the Ariina and Cyprinodonts, 

 which can pass with impunity through salt water, and are spread over much 

 larger areas. 



