508 EIGENMANN— ORIGIN OF FISHES OF THE 



Sternopygus macrurus found to the Atrato and Magdalena ; and 

 HopUas rnicrolepis which, aside from the Giiayas basin, is found 

 also in the Chagres. 



Of these four Sternopygus macrurus attains a much larger size 

 in the Guayas than elsewhere and may represent a variety distinct 

 from the nothern and eastern specimens. It is the only species 

 of the Guayas also found in the Magdalena and east of the Andes. 



Hoplias rnicrolepis disappears north of the Esmeraldas to re- 

 appear again in the Chagres. The entire region between is oc- 

 cupied by Hoplias malabaricus. 



Only four species extend south into Peru : Lebiasina bimaculata 

 and Bryconamericus pcruanus to the Rio Rimac, ^quidens rivula- 

 tus and Brycon atricaudatus to Pacasmayo. 



The remaining species are confined to the Guayas and the imme- 

 diate neighborhood. 



The 34 strictly fresh-water fishes belong to 28 genera (not count- 

 ing Gambusia and Ancistrus, which are in doubt) of which seven 

 (25 per cent.) are peculiar, Paracetopsis, Saccodon, Pseudochalceus, 

 Phenacobrycon, Landonia, Rhoadsia, Pseudopoecilia. All but one of 

 the rest of the genera, Microglanis, are also found in the north and 

 all but one, Lebiasina, east of the Andes. 



The Guayas fauna is as distinct from that of the Magdalena as 

 from that of the Amazon. It differs more from the fauna of the 

 Patia, emptying into the Pacific only a hundred miles north of the 

 Esmeraldas, than the Magdalena fauna differs from that east of the 

 Andes. 



Whence came the ancestors of the Guayas fishes? 



Pseudopxcilia, one of its peculiar genera, is of undoubted north- 

 ern derivation. Hoplias rnicrolepis, found elsewhere only in the 

 Chagres, and possibly Rhoadsia, scarcely distinct from Parastremma 

 which extends to Costa Rica, may also indicate that the ancestors of 

 these present genera came from the north. The probability seems, 

 however, equally great that they arose in the Guayas and moved 

 north or that the species both north and south are independent 

 developments from the fauna originally segregated from the east. 

 Pellegrin records a Pcecilia^^ from the Rio Pove. Whatever the 

 13 The name Pcecilia Pellegrini may be applied to this species. 



