of the Island of Trinidad, W. I. 407 



coalesce, forming a single row of large spots. Pectorals and 

 ventrals with single rows of spots between the rays. 



It attains a length of six to nine inches, and is occasionally 

 found a foot in length. 



A single dried individual of this species was brought from 

 Trinidad by M. Robin, and served for the description of that 

 species by M. Valenciennes. Other but smaller specimens 

 have been brought from the tributaries of the Rio de la Plata 

 by M. D'Orbigny, which M. Valenciennes was unable to dis- 

 tinguish from the species of Trinidad. M. Valenciennes 

 describes the interparietal plate as being destitute of a crest, 

 but with a slight convexity, and places it at the head of a 

 section, composed of species in which the angles and crests are 

 nearly obsolete, and the head and body become gradually de- 

 pressed. ~No mention is made of the blunt and obsolete ridges 

 and elevations noticed in the above description, but as our speci- 

 mens are from the same place as the one described by the 

 French ichthyologist, and agree in other respects, there can be 

 no doubt that they belong to the same species. 



If this fish has been correctly identified as belonging to the 

 same species as that found in the affluents of the La Plata, it 

 has certainly a most extensive range. 



Genus. 

 Ancistrus, Knee, (emend.) • 



Trunk slender and moderate, covered by several rows of 

 high and oblique, regularly imbricated plates, whose free mar- 

 gins are pectinated. Skin of abdomen entirely naked and 

 smooth. 



Head large, ovate, triangular, broader than the body. In- 

 terparietal with the breadth and length nearly equal. Eyes 

 moderate. Branchial apertures under the eyes. 



Interqpercirtum movable, and armed with a tuft of rather 



