104 MEMOIRS OF THE CARNEGIE MUSEUM 



only. It is a very aberrant Nematognath, with no relatives in other parts of South 

 America. It may be a remnant of the original forms. 



Pcecilocharax stands alone in the Characince, its only near relative being 

 Crenuchus, found in the Essequibo and Amazon. It also may be a left-over. 



This leaves Lithogenes villosus the only genus of the Loricariidce with the 

 armature reduced to a few prickles. Whether we regard this nakedness as primitive 

 or as secondarily acquired it points to a long separation from the other Loricariidce, 

 and Lithogenes may also be a left-over. 



The evidence seems, then, to favor the conclusion that the larger part of the 

 fauna of the upper Potaro has been more or less recently acquired, and that a 

 smaller part is composed of relicts of the original fauna of the Guiana Plateau. 

 This conclusion is, however, but tentative. Nothing is known about the fauna or 

 physical condition of the rest of the Guiana plateau except what follows under the 

 next head. The only other collections made were those of Richard Schomburgk, 

 and they were all lost. It is highly desirable, therefore, to collect about Roraima, 

 in the streams flowing in different directions. 



Fishes of the Ireng River. 



The following list may serve as a cross-reference to the preceding list of the 

 Upper Potaro. The names of species common to the Potaro and the Ireng are 

 here italicized. The Maripicru is a branch of the Ireng between Wontyke and 

 Karakara above the Karona Falls. Chipoo is between Karakara and the Rupununi 

 and is probably below the Karona Falls. The location of Nickaparoo was not 

 given me. 



The total list of species suggests that we may expect to find a number of 

 additional species in the Upper Potaro. 



Maripicru. Chipoo. Nickaparoo. 



1. Chasmocranus longior 3 



2. Rhamdia quelcn 3 8 



3. Trachycorystes galeatus 4 



4. Callichthys callichthys 1 1 



5. Hoplosternum thoracatum 1 



6. Plecostomus heniiurus 2 



7. Ancistrus temmincki 1 2 



8. Ancistrus cirrhosus. 1 



9. Loricariichthys stewarti 12 



10. Prochilodus maripicru 3 



1 1 . Parodon bifasciatus 1 



12. Chilodus punctatus 1 



13. Charicidium fasciatum 21 



14. Pyrrhulina filamcntusa 14 



15. Leporinus granti 9 



1 Near Holniia. 



