﻿Indiana University Studies 



BLOOMINGTON, INDIANA, March, 1913 



[Contributions from the Zoological Laboratory of Indiana University. No. 131.] 



Some Results from An Ichthyological Reconnaissance 

 of Colombia, South America. Part II. 



Carl H Eigenmann 



An account of the Colombian Expedition of December, 1912, 

 to April, 1913, was published in Part I of the present paper. 

 (Indiana University Bulletin, X, No. 8, Sept., 1912, issued Decem- 

 ber 23, 1912.) The questions of geographical distribution that 

 should find their solution in western Colombia and in Panama and 

 that led to the Colombian Expedition have been considered by 

 the present author in Science, N. S. XXII, July 7, 1905, pp. 18-20; 

 in the Popular Science Monthly, June, 1906, pp. 515-530; and 

 more fully in Reports of Princeton University Expedition, Pata- 

 gonia, III, 1910, pp. 225-511. The reconnaissance ou.tlined was 

 undertaken in large part as' a contribution to the solution of c|iies- 

 tions of the distribution of fishes. 



The first part of the present paper contained also descriptions 

 of thirty-one new species and four new genera of fishes. As an 

 introduction to the results of further studies on the material col- 

 lected, the article published in Science, now out of date, is repro- 

 duced in part. 



'The evidence collected indicates that the Pacific slope fauna of tropica', 

 America has been derived from the Atlantic slope fauna. Only three of 

 the genera of fresh-water fishes of the Pacific slope are peculiar to it ; 

 all the rest are identical with Atlantic slope genera. Even many species 

 are identical on the two sides. The indications are that in the main 

 the Pacific slope fauna was derived from the Atlantic slope fauna in 

 times much more recent than the obliteration of the interoceanic connec- 

 ' tion between the Pacific and Atlantic. An examination of the distribution 

 of the genera with representatives on the Pacific slope on the Atlantic side 

 of the continent shows that nearly all have a very wide range and are 

 found either in the Rio Magdalena or the Chagres. This indicates that 

 the present fresh-water fauna of the Pacific slope crossed the divide some- 

 where near Panama. It is to be borne in mind that a barrier which 

 may be ample to keep apart two marine faunas is not necessarily a bar- 



