SOUTH AMERICAN NEMATOGNATHI. 423 



ANALYSIS OF THE SPECIES OE PARA>'CISTIIUS. 



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

 spots; orbit 3 in the snout, 5^ in the head, 1| in the interorbital. Cau- 

 dal obliquely truncate. punctatissimus 391. 



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



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



nigricans 393. 



391. Parancistrus punctatissimus. 



"i Hypostomus 7iivealusC-Astelnan, Anim. Am. du Sud. 43, pi. xxi,fig. 



3, 1855 (Araguay; Goyaz). 

 ? Chcetostomus niveatus Gitnther, v, 243, 1864 (copied). 

 Chcetostomus punctatissimus Steindachner, Flussfische Siidam. ii, 



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

 Parancistrus punctatissi7mis 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 l-f in the width, 

 the width of the caudal peduncle 2| 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, 5| in the head, 1| in the 

 interorbital. 



Preopercle erectile, with slender bristles. 



Posthumeral keel obtuse. 



