100 



MEMOIRS OF THE CARNEGIE MUSEUM 



The numbers in the respective squares show the number of specimens taken 

 and thus indicate the relative abundance of the species at each place. 

 An analysis of this list shows three groups of species. 



a. Very widely distributed species: 1, 4, 7, 9, 11, 12, 14, 15, 16, 17, 18, 21. 

 All of these are found in the neighboring river Ireng, of the Amazon basin. All of 

 these are also found below the Kaieteur, but in different proportions. The per- 

 centage of the total fauna of the plateau formed by this group is 56.60. 



b. Peculiar species of very widely distributed genera. 



(1) Confined to the plateau: 3, 13, 19 = 13.01 per cent. 



(2) Found also below the Kaieteur: 10, 20, 22 = 13.01 per cent. 



c. Peculiar genera and species. 



(1) Peculiar to the plateau: 5, 6 = 8.69 per cent. 



(2) Found both above and below the Kaieteur, but confined to the Potaro 

 (?): 2, 8 = 8.69 per cent. 



A. If this fauna is the nucleus of the original undifferentiated fauna of South 

 America we are at once confronted by the fact that 56.60 per cent, of the species 

 are identical with species now found everywhere, and 26.02 per cent, consist of 

 species belonging to genera of the widest distribution in South America. The 



