98 MEMOIRS OF THE CARNEGIE MUSEUM 



Sci^NiD^. 138. Heterogramma steindachneri A 



130. Pachyurus schomburgki A 139. Cichla ocellaris A 



CicHLiD/E ^^^" Crenicichla alta ABC 



131. Nannocara bimaculata B ^^l. Crenicichla wallacei A 

 132.*^quidens geayi A B 142. Crenicichla lugubris ABC 



133. Mquidms potaroensis ABC l^^- Crenicichla Johanna A 



134. Cichlasoma severum B Soleid^. 



135. Geophagus surinamensis A 144. Achiurus lineatus A 



136. Biotodoma cupido A 145.**Seleonasus finis A 



137. Heterogramma ortmanni (A?) B (C?) 



Of these, Poecilurichthys bimaculatus, Hypopomus brevirostris, and Callichthys 

 callichthys have not been taken in the Potaro below the Kaieteur, but, inasmuch 

 as they are found on the plateau and in the Essequibo, they probably also occur in 

 the lower Potaro, and are so rated. 



The table on page 99 summarizes the different categories in the preceding list. 



In this table the first column represents the species found below the Kaieteur, 

 and it will be seen that while there are one hundred and forty species found in this 

 part of the river, there are but twenty-three above the Kaieteur. 



It is, however, not fair to compare the fauna of the plateau with the fauna 

 of the entire lower Potaro, because the fishes of the Essequibo can easily ascend to 

 Tumatumari. The cataract at Tumatumari is probably not an effective barrier 

 to many fishes. There is a more difficult series of cataracts between Potaro Landing 

 and Kangaruma, and another cataract at Amatuk. The cataract at Waratuk, like 

 that of Tumatumari, may be left out of account. Jiy comparing the fauna as 

 determined in the three lower divisions of the Potaro it is seen that only seventy- 

 six species (B and C) are found above Kangaruma. The rest, with very few excep- 

 tions, are fishes of the lower and middle Essequibo. Evidently species that are 

 not able to ascend the Potaro Landing cataracts need not be expected on the plateau. 



By further restricting the vision we find that onl.y thirty-six species have so 

 far been taken above the Amatuk Cataract. This is certainly not all of the species 

 found in this area, but the number indicates that there is a distinct reduction in the 

 number of species as compared with the Potaro at Tumatumari. 



Further investigations should be made of the fauna of the Potaro above the 

 Amatuk cataract and above the Kaieteur. Eight species found above the Kaieteur 

 and in the Essequibo, but not taken in C, should probably be added to the thirty-six 

 actually captured. It would seem from these lists that the groups extending to 

 the base of the Kaieteur, but not found above it, are the Curimatinse, Hemiodinse, 

 Nannostomatinse, Leporininae, Bryconinse, Gasteropelicinae and Acestrorhynchinse. 



