SOUTH AMERICAN NEMATOGNATHI. 419 



380, Hemiancistrus scaphirhynchus, 



Ancistrus scaphirhynchus Kner, Hypostomiden, 280, pi. iii, fig. 2 



(Barra do Eio Negro). 



Chcetostomus scaphirhynchus Giinther, v, 244, 1846 (copied). 

 Hemiancistrus scaphirhynchus Eigenm. & Eigenm. Proc. Cal. Acad. 



2d Ser. ii, 43, 1889 (Hyanuary; Coary; Teffe; Hyavary). 

 Habitat: Solimoens. 



Long, slender, depressed, the depth little more than 

 half the width. Head broad, its sides almost vertical at 

 the orbit; margin of the orbit slightly raised, a groove 

 behind the eye; bones of the head regularly grooved; oc- 

 cipital bordered by 3-5 nuchal plates; post-temporal plates 

 forming half of the upper and a portion of the posterior 

 margin of the orbit, the suborbital bone forming the re- 

 mainder of the posterior margin; frontal plates with a 

 triangular lateral expansion which reaches the orbit. 



Margin of the snout with short bristles. 



Orbit 4 in the snout, 7 in the head, 3J in the interor- 

 bital. 



Preopercle and opercle erectile, the preopercle with a 

 bunch of spines, the longest of which is longer than the 

 orbit; opercle with a marginal series of short, fixed spines. 



Lips broad, sparingly papillose; teeth very fine. 



Barbel rudimentary. 



Ventral surface of body and head naked. 



Dorsal scutes striate, not, or scarcely keeled; lateral 

 scutes keeled, the keels becoming strongest above the 

 anal. Posthumeral keel not prominent. 



Distance of the dorsal fin from tip of snout 2| in the 

 length. Base of the dorsal fin equals its distance from 

 the posterior margin of the adipose fin. Last dorsal ray 

 little lower than the first. 



Caudal fin obliquely truncate, the lower lobe produced. 



Upper surface of the pectoral spine thickly covered 

 with fine cardiform bristles, which are longest in the 6 . 



Light or dark brown with indistinct lighter spots; fins 

 obscurely banded. 



