340 PATAGONIAN EXPEDITIONS I ZOOLOGY. 



region. It came from the north, in small part from the eastern plateau, 

 in greater part from the Amazon valley. The question of the time of 

 the origin of the fauna is of interest. The only observations, as far as I 

 know, directly bearing on this question are those of A. Smith Woodward, 

 1900, who recorded from . the Parana formation fragments of ''Arius, 

 Pimelodits, Platystomns and other genera which still live in the freshwaters 

 of South America" and also fragments of characinoids. The formation 

 is a marine deposit, near the city of Parana, which he thinks "is truly of 

 late Tertiary age, and may probably be correlated with the Pliocene of the 

 northern hemisphere." As these deposits contain remains of land-mam- 

 mals, sharks' teeth and fresh-water fishes it is probably an estuary deposit 

 of the former mouth of the Parana river. The present fauna of this 

 stream developed with the stream itself 



List of Fishes Recorded from the Paraguay Basin. 



In the following list, "*" indicates that the species is peculiar to the 

 Paraguay basin; " ** " that both the genus and species are peculiar; 

 "A" indicates that the species is also found in the Amazon basin; "a" the 

 genus is found in the Amazon basin ; and "/" that the species is peculiar 

 to the La Plata. "C" that it is also found in the coast streams of Eastern 

 Brazil and "S" that it is also found in the San Francisco. 



A Potamotrygon hystrix Miiller & Troschel. 



A Potainotvygon dumerilii Castelnau. 



a* DysicJitJiys australe Eigenmann & Ward. 



a* Bwwcephahis vugosns Eigenmann & Kennedy. 



a / Btinocephalus ihevingii Boulenger. 



a* Bnnocephahis doricB Boulenger. 



A Pinarampns pirinampii (Spix). 



A Luciopimelodns platanus Gunther. 

 AS Psendopinielodits zungaro (Humboldt). 



* Psendopinielodits cottoides Boulenger. 

 / Heptapfenis niitstelinus Valenciennes. 



AC RJianidia quelen (Quoy & Gaimard). 

 K RJianidia sebcB kneri Steindachner. 

 A Pimelodits ornata Kner. 



* Pimelodits albicans (Cuvier & Valenciennes). 

 AS Pimelodits clarias (Bloch). 



