41 6 Evolution and Distribution of Fishes 



two ancient genera intermediate between the Salmonidae 

 and Percesoces. 



In reviewing the above, and the evidence furnished by 

 the accompanying chart (Fig. 69), the writer concludes 

 that the Siluridae evolved in central America or northern 

 S. America during late Cretaceous time, that extensive mi- 

 gration into N. America took place later, when many sub- 

 tropical plants and animals also moved into the U. S. and 

 even Canada; that an early and important migration from 

 N. E. Brazil and Guiana along the S. Atlantis continent In- 

 troduced types into western, central and later east Africa. 

 Eastward penetration along the Indo-Mascarene land-mass 

 ensured invasion ultimately as far as the E. Indian Archi- 

 pelago. Meanwhile through adaptation to a brakish life, 

 and later to a shore life, the sea catfishes — Arius, Galeich- 

 thys, and Aelurichthys — branched off from more ancient 

 types, specially in S. America and the E. Indies. Such dis- 

 tributions yield added and confirmatory proof, that only 

 with acceptance of the existence of past geologic land 



Fig. 69. Chart showing present and probable past distributional 

 area occupied by Siluridae. The arrows indicate pathways follow- 

 ed, these in a few cases leading to an acquired marine life. 



