PACIFIC SLOPE OF ECUADOR, PERU AND CHILI. 511 



Leporinus from the east. 



Piabucina from the north? 



Hyphessobrycon from the east. 



Astyanax from the east. 



Phcnacobrycon . from the north or east. 

 Bryconamericiis . from the north or east. 

 Pseudochalceus . from the east. 



Landonia from the east. 



Brycon from the north or east. 



Hemibrycon .... from the east. 



Rhoadsia from the east. 



Hoplias from the north or east. 



Sternopygus ....from the (north or?) east. 

 Pseudopcecilia . . . from the north. 



Gauibusia}^ from the north. 



JEquidens from the north or east. 



Cichlasoma from the north or east. 



I have formerly expressed the opinion that the Guayas fauna 

 probably came from the Amazon basin east of it.^' This explana- 

 tion has been greatly strengthened for part of the fauna by the 

 present study. This part may have been segregated from the 

 Amazon fauna as the Magdalena fauna was later segregated from 

 the fauna of the present Orinoco basin. The present study also 

 furnishes some evidence that in times more remote than the origin of 

 the present San Juan fauna part of the Guayas fauna (Hoplias 

 microlepis may have been derived from the north. If so, the fauna 

 between the Patia and the Canal Zone was subsequently obliterated 

 and the area between Panama and the Patia became repopulated 

 later by way of the Atrato and San Juan, the Guayas fauna remain- 

 ing intact all the while and containing Hoplias microlepis, Lepori- 

 nus, and Prochilodus, which have not been able to enter the territory 

 between the Atrato and the Mira. 



At present the Guayas fauna is more dififerent from that of the 

 Magdalena on the same side of the Andes than that of the Magdalena 

 is from that of the Orinoco basin across the high Andes of Bogota. 



When and where the derivatives from the Amazon came across 



^^ In the Esmeraldas or Guayas ? It was recorded from the Rio Pove. 

 "^"^ A reservation must be made for Basilichthys which is a Chilian genus 

 ranging north at least to the Rimac. 



