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226 PATAGONIAN EXPEDITIONS: ZOOLOGY. 



the three types mentioned have undergone unparalleled adaptive radiation 

 in the growing and metamorphosing continent, the Cichlids developing 

 about 150 known species, the Characins 500, besides differentiating the 

 Gymnotids, and the Catfishes, 500 or more species, distributed in several 

 autochthonous families. 



The grounds for all of these conclusions together with their corollaries 

 you will find set forth in detail, all of which I hope will meet with your 

 approval. 



This report is divided therefore into a section dealing with The Fresh- 

 water Fishes of Patagonia, a section dealing with the Archiplata-Archhelenis 

 theory and a section listing all of the fresh-water fishes of South and Middle 

 America. 



I must at this place acknowledge the most courteous assistance received 

 from Mr. Richard Rathbun and Mr. Barton A. Bean, of the United States 

 National Museum ; Dr. G. A. Boulenger and Mr. C. T. Regan, of the 

 British Museum ; Dr. Franz Steindachner, of the K. K. Museum of Vienna ; 

 Mr. S. Henshaw, of the Museum of Comparative Zoology, and Dr. R. 

 Gestro, of the Museo Civico di Storia Naturale, Genoa, Italy. 



Respectfully submitted, 



Carl H. Eigenmann, 

 Professor of Zoology, Indiana University, and Director of 



the Indiana University Biological Station. 



