510 EIGENMANN— ORIGIN OF FISHES OF THE 



dontinge found both in Colombia and east of the Andes. It does 

 not help us to solve the question of the origin of the Guayas fauna. 



Another genus of importance is Lehiasina, a recent derivative of 

 Piabuchia, into which it still merges. Piabiicina is found both in 

 Colombia, Venezuela, and in eastern Ecuador. The ancestors of 

 some of the species of Piabucina in Colombia may have come from 

 Venezuela and those of Ecuador may have come independently 

 from the Amazon. 



The fauna of the Guayas is certainly quite distinct from that 

 of western Colombia. 



South of the Guayas basin the question has simply been which 

 of the Guayas species originally segregated have been able to live or 

 survive in the unfavorable conditions offered by the desert slopes of 

 Peru.i* 



The fauna of Peru is a fauna of relicts. Of the nine species 

 in the Jequetepeque, four are found in the Guayas. Of the five 

 species of the Rimac, two are found in the Guayas, one is Chilian, 

 one belongs to the high Andes, and one is a local form of a genus 

 found in the Guayas. 



List of the Guayas Genera and their Probable Derivation or 

 THE Probable Derivation of their Ancestors. 



Paracetopsis .... from the east. 

 Micro glanis .... from the east. 



Rhamdia from the north or east. Originally from the east. 



Pimelodella from the north or east. Originally from the east. 



Plccostomns .... from the east. 



H einiancistrus . . from the north or east. 



Ancistrus^^ from the east. 



ChcEtostomus . . . from the north or east. 



Curimatus from the east. 



Apareiodon .... from, the east. 



Saccodon from the east. 



Prochilodus from the east. 



1* I have elsewhere described how at Piura the water in the Rio Piura 

 during the dry season was restricted to a few pools around the pier of the 

 bridge, around some rocks, etc., and how the fauna was concentrated in 

 these pools where the individuals were starved to the point of death. 



15 In the Esmeraldas or Guayas? 



