The Soft-finned Teleostei 351 



revealed to science. The majority of the genera and species 

 are S. American, rarely Central American, but many are 

 widely extended over a large part of i\frica. Their extension 

 eastward was probably effected at a time when by enormous 

 faulting and volcanic action, the sea was encroaching on, 

 and breaking up the eastern or "Lemuria" part of Gond- 

 wana into a western African half, and a south-eastern 

 Asiatic half. So while they reached Africa, they failed 

 to pass further eastward. On the whole the African genera 

 and species are more highly modified from the average type, 

 than are the American. 



The remarkable family Gymnotidae, or the group of 

 electric eels, is now generally accepted as a specialized off- 

 shoot from the Characinidae. But alike from structure, 

 evolutionary relations, and distribution, it suggests deriva- 

 tion from a form intermediate between Characinidae and 

 Siluridae, and Which gradually spread southward from 

 Central America. It is now represented by upward of 30 

 species that inhabit lakes and rivers of S. America. 



The Cyprinidae is "the largest of all the families of fish- 

 es, comprising 200 genera and 2000 species found through- 

 out the North Temperate zone, but not extending to the 

 Arctic circle on the North, nor much beyond the tropic of 

 Cancer on the south." Amyzon, of early Eocene age, is 

 known from strata of the Western States by four or five 

 species, while in individuals it must often have been extreme- 

 ly abundant. Diastichiis, Gohio, and Leuciscus succeeded, 

 as members of the family spread eastward into Europe, 

 while Thynnichthys and Barhus evolved as east Asiatic 

 genera. Such distribution would suggest that during late Cre- 

 taceous or early Eocene time, land connection existed from 

 Western N. America across to eastern Asia. But the exist- 

 ence also of about 100 species in Africa indicates that num- 

 erous derivative types from those that entered N. E. Asia, 

 had spread westward alike into East Europe and Africa. 



From the abundance of fossil individuals as well as 

 species of such genera as Tinea, Leuciscus, Rhodeus etc., 

 as described by Reuss and Meyer {188: ^()), also by 

 Winkler (2^9 : 16), the cyprinoids attained to a dominant 

 freshwater position during the Miocene age. 



