159 



DARK CENTRA RCHUS. 



Cmtrarchus niger. 



PLATE XII. 



Of this species we do not possess available Notes, 

 and a representation of the drawing is given to 

 complete the Ichthyology of the Guianese waters so 

 far as our materials will allow, and to call the at- 

 tention of other travellers to the wanting points. 

 The figure of this fish is in length six inches and 

 three-quarters, in depth about three ; the colour is 

 entirely a dark bluish black, paler beneath ; and on 

 the belly, anterior to the ventral fins, the edges of 

 the mouth, and the borders of the opercula and pre- 

 opercula, indigo blue; the iris is coloured orange- 

 red ; the dorsal fin is represented as having seventeen 

 spiny rays, ten soft; the ventral with six spiny, 

 eight soft, and both without any appearance of 

 spotting. The ventral fin has a strong round spine 

 before the first soft ray, which considerably exceeds 

 the others in length. Taken in the Rio Negro in 

 February. 



