EIGENMANN! THE FRESHWATER FISHES OF BRITISH GUIANA 



73 



Of the four hundred and ninety-three species enumerated in the preceding list 

 all but twenty-three, which are recorded from the Rio Branco only, inhabit the 

 northward-flowing streams from the Orinoco on the west to the Brazilian boundary 

 on the east. Of these two hundred and forty, or over 50 per cent., are also found 

 in the Amazon. 



In the Rio Branco, the only stream of the Guianas flowing southward which 

 has been examined, twenty-three species have been taken, aside from those which 

 it has in common with the upper Essequibo. The more readily to show the relation 

 of the Rio Branco to the Rupununi and upper Essequibo, the fauna of the Essequibo 

 is divided into (4) the fauna of the Essequibo above the Warraputa Cataract, (5) 

 the fauna below the Warraputa, (6) the fauna of the lower Potaro, (7) the fauna of 

 the upper Potaro. 



From the Essequibo basin two hundred and sixty-six species have been taken, 

 and this number may serve as a measure of our information, or lack of information, 

 about the inhabitants of the other streams. From the large Orinoco basin but 

 eighty-nine species have been recorded. 



Distribution of the Species Obtained in the Area Examined. 



The maps, given in Plates LXXI-CIII inclusive, graphically show the points 

 at which the commoner species characteristic of the fauna were taken. A refer- 

 ence to these maps will, I trust, be useful to the student who is interested in the 

 question of distribution. 



