FISilES OF SOUTH AND MIDDLE AMEBIC! 523 



tribntion. If there was a continental mass connecting South America 

 with New Zealand and Australia tit to be inhabited by fishes, there must 

 have been an abundant and diverse fish fauna which has disappeared. 

 If the antarctic continent depended entirely for its existence on the 

 evidence from the distribution of the fresh-water fishes, its existence 

 would be very highly theoretical and precarious. 



However, the evidence from other sources of a former land con- 

 nection has become conclusive, and T am of the opinion that during 

 the submergence of large parts of Patagonia during the late Pliocene the 

 formerly abundant fresh-water fauna became exterminated, with the 

 exception of those that were indifferently fresh-water or marine. 



The Petromyzontidre offer still another difficulty. There* is no 

 place on the American continents between the Mexican plateau and 

 Central Chile that harbors any species of the family. The northern 

 and southern species belong to distinct genera. At least two of the 

 South American genera are peculiar while two others are found in 

 Australia and New Zealand. 



8. The Similarity of the Tropical American to the Tropical African 



Fauna and the Necessity of and Evidence for a Former 



Land Connection between Africa and, South America. 



North America has not contributed a single element to the fresh- 

 water fish fauna of South America. Two prominent South American 

 families, the Characiniclae and the Cichlidae, have representatives as far 

 north as the Rio Grande basin, and one of these has succeeded in 

 crossing over into Cuba, evidently from Yucatan; on the other hand, 

 several members of the North American fauna have representatives as 

 far south as the Isthmus of Tehuantepec. The North American fauna 

 is entirely distinct from the tropical American fauna. 



But four genera of fresh-water fishes of South America north of 

 Patagonia are found in any other continent than North America. 

 These are Synbranchus, Agonostomus, Cotylopus and Fundulus. The 

 first found also in brackish water, the second belonging to the marine 

 family, Mugilida\ and the others to the Pceciliidse. Synbranchus is 

 found in India, Agonostomus in middle America, the West Indies, 

 northern South America and New Zealand, Australia, Celebes, 

 Mauritius and Comoro Islands. There is no reason why Agonostomus 

 may not have been independently evolved in the South Sea and in 

 America from marine Mugilids. Cotylopus is found in Central 

 America and Reunion and Fundulus in America and Europe. 



It is possible that Pimelodus is found in Africa and Pseudauchenip- 

 tcrus in Madagascar. Both are found in South America. 



Africa and South America have two groups of families in common. 

 The first group comprises the Serranida.', Scisenidae, Mugilida? and 

 Tetraodontida?. 



