THE FISHES OF SOUTH AMERICA 
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:}: 
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. Regan § 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. 
t 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. 
