

j^. ^^^i^^% 



PART III. 



THE FRESH-WATER FISHES OF PATAGONIA AND 



AN EXAMINATION OF THE ARCHIPLATA-- 



ARCHHELENIS THEORY. 



BY 



CARL H. EIGENMANN, 



Indiana University. 

 Professor W. B. Scott, 



Princeton, New Jersey. 



Dear Sir : I enclose the MS. of my report on the fishes collected by 

 the late J. B. Hatcher in Patagonia. Instead of confining my report to 

 the few specimens collected by Mr. Hatcher I have utilized, as far as pos- 

 sible, the knowledge gained from previous collections, and have dealt 

 monographically with the fresh-water fishes of the area south of the line 

 joining the mouth of the Rio Negro and Santiago, Chili. Ichthyolog- 

 ically this area constitutes a faunal unit sharply defined from temperate 

 and tropical America to the north of it. 



Since 1887 I have been busied more or less with the fresh-water fishes 

 of South America, and the present opportunity seemed to me the best to 

 use our knowledge concerning them to test the claims of the Archiplata- 

 Archhelenis theory. This theory must stand or fall by the evidence of 

 the fresh-water fishes. The task proved much more onerous than ex- 

 pected, but I feel amply repaid by the definite ideas gained by this 

 review. 



It seems quite certain : [a) that tropical America obtained the elements 

 of its fauna in common with Africa before the Tertiaries, from some insig- 

 nificant common ground inhabited by Cichlids, Characins, and Catfishes 

 (Nematognaths) and perhaps types of wide distribution which remain only 

 as relicts ; ib) that tropical America has not been accessible and received 

 few, if any, immigrants from other land areas since that time ; but [c) that 



225 



