eigenmann: the FRESHWATER FISHES OF BRITISH GUIANA 63 



"Unfortunately little is known of the fauna of the streams of the table land of 

 Guiana, the region where the remnant of the original fauna -may be expected to 

 persist. Schomburgk's collections made in those streams were largely lost. He 

 states that it was rich in species (over 30). 



"Andre ('A Naturalist in the Guianas,' p. 205) says: 'In fact the falls of Para 

 [of the Caura] appear to constitute an effective barrier between distinct forms of 

 river life', and that the fauna above the falls is different from that below. 



"The most promising field for scientific results, if not number of species, seems 

 to me to be offered by the rivers of this region, which should be explored above and 

 below falls that are impassable barriers for the ascent of fishes. 



"The rivers of this region, exclusive of the northern tributaries of the Amazon, 

 concerning which not much is known, contain a total of about 298 recorded species. 

 Of these about 60 per cent, are also found in the Amazon; as of these about 16 

 species are from the Rio Branco basin and not from the other streams and the Rio 

 Branco belongs to the Amazon system, this number must be reduced by 16, which 

 still leaves over 50 per cent, of the fauna identical with that of the Amazon." 



The following table is derived from the one succeeding the above quotation. 

 It is condensed laterally by including the tributaries of the Branco and the rivers 

 of French and Dutch Guiana in one column each, and is expanded vertically by add- 

 ing the species discovered by me. 



It will especially show the relation of the fauna of the Essequibo to that of 

 adjoining regions. Columns 1, 2, 5, 8, 9 and 10 offer an opportunity for a com- 

 parison of the lowland faunas from west to east, i. e., of the Orinoco, Barima, 

 lower Essequibo, Demerara-Mahaica, Surinam, and French Guiana. Columns 3, 4, 5, 

 6 and 7 offer an opportunity for a comparison of the fauna of the Lower Essequibo 

 (5) from its mouth to the Warraputa Cataracts with that of the Upper Essequibo 

 and its tributary the Rupununi (4) and with that of the lower Potaro (6) and upper 

 Potaro (7), and also the Rio Branco (3) with its tributaries, the Ireng, et al. The 

 details of the distribution of the British Guiana species are taken up later. Those 

 species found also in the Amazon are preceded by an A. Those species preceded 

 by an L are also found in the La Plata system. Those peculiar to the Guianas 

 are marked with an *, and the genera peculiar to the region are marked with a 

 double **. The estuarine species are preceded by an M. 



In the following table column 1 represents the Orinoco basin, 2 the streams 

 emptying between the Orinoco and the Essequibo, 3 the Rio Branco basin, Takutu, 

 Ireng et al., 4 the upper Essequibo with the Rupununi, 5 the Essequibo below 

 Warraputa, 6 the lower Potaro, 7 the upper Potaro, 8 the Demerara, 9 Dutch 

 Guiana, especially Surinam, and 10 French Guiana. 



