SOUTH AMERICAN NEMATOGNATHI. 423 



ANALYSIS OF THE SPECIES OF PARANCISTBUS. 



a. Head, body and all the fins with numerous white (sky blue in life) 

 spots; orbit 3 in the snout, 5 in the head, If in the interorbital. Cau- 

 dal obliquely truncate. punctatissimus 391. 



aa. Orange yellow, borders of the fins carmine. aurantiacus 392. 



aaa. Uniform dusky, dorsal somewhat lighter; caudal obliquely truncate. 



nigricans 393. 



391. Parancistrus punctatissimus. 



? Hypostomus niveatus Castelnau, Anirn. Am. du Sud. 43, pi. xxi,fig. 



3, 1855 (Araguay; Goyaz). 



? ChcKtostomus niveatus Giinther, v, 243, 1864 (copied). 

 Chcetostomus punctatissimus Steindachner, Flussfische Siidam. ii, 



19, pi. iii, figs. 3-3a, 1881 (Amazon). 

 Parancistrus punctatissimus Eigenm. & Eigenm. Proc. Cal. Acad. 



2d Ser. ii, 44, 1889 (Porto do Moz). 

 Habitat: Amazon and its tributaries. 



H. niveatus is most probably identical with punctatis- 

 simus, but a positive identification is impossible from 

 Castelnau's plate and description. 



Short, depressed anteriorly, becoming compressed on 

 the tail, the depth at origin of dorsal fin If in the width, 

 the width of the caudal peduncle 2J in its depth. Head 

 depressed, its depth nearly 2 in its greatest length; pro- 

 file not steep, the interorbital little concave; occipital 

 bone ending in a short process, the margins of which 

 are slightly concave, its apex forming an obtuse angle; 

 3 nuchal plates bordering the occipital. Bones of the 

 head and all the scutes rough with minute bristles or 

 spines, not keeled. Sides of the head and snout granu- 

 lar, a rather broad naked area at the tip of the snout; 

 no tentacles on the snout; a maxillary barbel about as 

 long as the eye. 



Teeth slender, bicuspid. 



Ventral surface entirely naked, the abdomen villous. 



Orbit about 3 in the snout, 5J in the head, 1^ in the 

 interorbital. 



Preopercle erectile, with slender bristles. 



Posthumeral keel obtuse. 



