424 Evolution and Distribution of Fishes 



the S. Atlantis bridge, of a few species of Tetragonopteriis 

 in late Eocene time, that would start the subsequent evolu- 

 tion there of Alestes, Petersius, etc.; also of Cynodon and 

 Xiphostoma that would start the evolution of related Afri- 

 can forms like Hydrocyon and Sarcodaces. 



While these were in process of evolution over the 

 Central African plateau, those extensive "eurycolpic" folds, 

 faults, upheavals, and depressions occurred, probably dur- 

 ing Miocene time, that equally obliterated connection of 

 Africa with S. America, and that gave rise to, or certainly 

 accentuated, those rift valleys like Lake Tanganyika, the 

 Nile valley, the Red Sea, and lesser valleys. Since that time 

 continued steady uplift from the "Great Western range," 

 has given rise to the localized areas, in which species and 

 genera peculiar to each region have evolved. 



In brief summary then the writer would set forth, that 

 the Characlnidae first arose in the north-central part of 

 S. America, and during mid or late Cretaceous times. 

 Gradually spreading and breaking up into evolving species 

 and genera, these by Eocene times, had invaded the conti- 

 nent from eastern coast to western, while as yet the Andean 

 upliftings and foldings had advanced little. But, as these 

 became increasingly pronounced, a pacific or western series 

 became separated from the eastern types, while migration 

 northward of outliers Into Central and Mexican America 

 proceeded. Meanwhile a few derivative species were 

 carried across river or swamp areas of South Atlantis into 

 west Africa during Eocene times, and multiplying there 

 were carried across the African continent, from Senegal and 

 Gaboon to the Upper Nile and the Zambesi. These In turn 

 Were In considerable part obliterated during the tremendous 

 earth disturbances that gave rise to the higher Andes, to 

 the Great African Range, that destroyed the South Atlantis 

 bridge, and that formed or assuredly accentuated the Afri- 

 can rifts or "graben." The high eastern face of the Nile 

 and the Red Sea ravine-wall, prevented further migration 

 eastward after early Pliocene times. 



The highly modified family Gymnotidae is now generally 

 accepted by ichthyologists as a derivative group from the 

 last. Its restriction to Central and South America, and its 



