SOUTH AMERICAN NEMATOGNATHI. 271 



Centromochlus (Glanidium) albescens Steindachner, SB. Ak. Wien, 

 Ixxiv, 1876, Siisswasserfische siidostl. Bras, iii, 106 (Rio Para- 

 hyba. 



Habitat: Coast streams from Rio Janeiro to the Amazon. 



Body about as wide as deep, compressed toward the 

 caudal fin. Head broad, depressed, flattish above in the 

 adult, its width little less than its length, its depth 1J 

 in its length; surface of the bones roughened but every- 

 where covered with skin. Dorsal plate with an outward- 

 projecting process behind. Fontanel elongate ; snout 

 abruptly decurved, broadly rounded in front. Space 

 between anterior and posterior nares little less than the 

 diameter of the eye. 



Eye lateral, 4-5 in the head, 2J-3 in the interocular. 



Maxillary barbel reaching beyond the tip of the hu- 

 meral process; mental barbels short. 



Jaws equal, the mouth terminal; teeth villiform, the 

 intermaxillary band about eight times as broad as deep. 

 Humeral process extending somewhat beyond middle of 

 pectoral spine. Pectoral pore wanting. 



Lateral line straight. 



Distance of dorsal spine from snout 3 in the length; 

 dorsal spine short, smooth or slightly roughened on 

 both margins, 1J-2 in the head. 



Caudal forked, 4-4f in the length. 



Base of the anal rather long, 2J-2f in the head. 



Ventrals not reaching the anal. 



Pectoral spine short and stout; its sides finely striate, 

 the inner margin entirely dentate, the outer margin 

 smooth 011 its basal half, with teeth 011 the upper half. 



Ventral surface white, sometimes with a few dots on 

 the chin; sides grayish, becoming darker on the dorsal 

 surface; sides and back covered with dark dots which 

 are aggregated into spots in places; basal third of the 

 caudal fin yellowish, abruptly dusky or black behind; 

 other fins more or less dotted and spotted with black, 

 the dorsal always darkest. 



