379 



researches have shown that these extinct forms all belong 

 to the genus Ceratodus, that all are members of the family 

 Ceratodidae.* The only fossil member of the Lepidosirenidae 

 is Protopterus libycus of Egypt. There is really no reason, 

 therefore, as Dr. Boulenger f puts it, why the latter family 

 should not have passed from one of the two continents into the 

 other when they were connected by land. 



Another striking feature of the South American fresh-water 

 fish fauna is the extraordinary number and variety of forms 

 of the Characinidae, unquestionably, according to Dr. Bou- 

 lenger, one of the most lowly and generalised groups of ex- 

 clusively fresh-water teleosts. They are likewise abundantly 

 represented in western and central Africa, yet not a single 

 genus is common to both continents. Hence Dr. Boulenger J 

 concludes that it is quite legitimate to explain the distribu- 

 tion of this family by the assumption of a land bridge con- 

 necting Africa and South America about the end of the 

 Cretaceous Period. 



A similar argument is used by Mr. Began to account for 

 the large fresh-water family Cichlidae (compare Fig. 12) in 

 these two continents, except that he is of opinion that the 

 land bridge was still in existence in early Eocene times. 



Professor Eigenmann || states that there is no known means 

 by which these two families could have crossed the existing 

 gap between Africa and South America. There has been no 

 exchange of species in recent times, for there is no species 

 or genus common to the two continents. The South American 

 and African elements of these two families must have been 

 derived from some intermediate land-mass, or must have 

 travelled from one continent to the other over a land bridge. 

 That this connection must have been obliterated before the 

 Tertiary Era is evidenced, he remarks, by the fact that the 

 Tertiary deposits of Taubate and Parana include existing 

 genera, and that many South American families of fishes 



* Goodrich, E. S., " Cyclostomes and Fishes," p. 258. 

 t Boulenger, G. A., " Distribution of African Fishes," p. 5. 

 J Boulenger, G. A., " Distribution of African Fishes," p. 6. 

 Began, T., " Fishes of Central America," p. xiv. 

 || Eigenmann, C., " Fishes of South and Middle America," pp. 525 

 526. 



