506 EIGENMANN— ORIGIN OF FISHES OF THE 



farther south the Jequetepeque, Rimac, etc., flow from the Cor- 

 dilleras directly to the sea. The Guayas basin lies between the great 

 coastal desert of Peru and the extremely wet region of southern 

 Colombia. It is the largest river basin of the Pacific slope north of 

 Chili. 



The fish-fauna of the Guayas basin is old and highly specialized. 

 It gradually tapers ofiE southward as one and another genus and 

 species have been excluded or exterminated by the elevation of the 

 Andes, resulting in torrential courses, high seasonal variation in the 

 amount of water a;nd great fluctuations in the amount of silt carried, 

 all conditions unfavorable to fishes. 



The fishes on the Pacific slope of Colombia are quite distinct 

 from those of Ecuador and Peru. 



The fishes of the Patia, in southern Colombia, are essentially 

 like those of the San Juan, in central Colombia. On the other 

 hand, the fishes of the Guayas and the San Juan basins, the former 

 in the wet zone, the latter in the dry zone, are essentially different. 

 The line separating the two faunas lies somewhere near the Mira 

 and Esmeraldas basins. 



Little is known of the fishes of the Esmeraldas. Several no- 

 table contributions to the fauna of the Guayas have been published. 

 One of these is Kner and Steindachner's " Neue Gattungen und 

 Arten von Fischen aus Central-America gesammelt von Prof. Moritz 

 Wagner" (Abhandl. k. bayer. Akad. Wiss., Miinchen, X., 1864). 

 The general bearing of the facts was discussed by Wagner, in the 

 same volume, pp. 93-109. Another is Steindachner's " Zur Fisch- 

 Fauna des Cauca und der Flusse bei Guayaquil " (Denksch. K. 

 Akad. Wiss., Wien, XLII., 1880, pp. 55-104, 9 plates). 



A third contribution of note to this region is: Boulenger's 

 Poissons de I'Equateur."^ 



In this paper Boulenger describes or lists the specimens collected 

 by Festa in a trip across southern Ecuador from Santa Elena 

 through the Guayas basin to the Rios Zamora, Santiago and Bam- 

 boiza rivers. The last three are parts of one system tributary to the 



" Viaggio del Dr. Enrico Festa nell'Ecuador e regione vicine," Bolletino, 

 Musei Zool. Anat. comp. delta Univ. di Torino (Premiere Partie), XIII., 

 No. 329, Dec. 2, 1898; (Deuxieme Partie), XIV., No. 335, Feb. 15, 1899. 



