156 Proceedings of the Biological Society of Washington. 



Apical field with numerous sharp isolated teeth in about four rows, one 

 of which is marginal ; base broadly rounded, with rather coarse cir- 

 culi, and no radii; nucleus central. The arrangement of the teeth 

 reminds one of the Macruridse. 



Cynopolamus argenteus Val., Paraguay (Page) ; U. S. N. M. 



No such teeth in apical field; scale cycloid 1. 



1. Apical field with many radii, between which the circuli are very 



coarse and widely spaced, in complete contrast with those of the 

 base and sides of the scale; scale about 4.75 mm. long and 6 

 broad; laterobasal corners rounded; no basal radii. System of 

 circuli like that of the African genus Sarcodaces 



Salminus maxillosus C. & V. Paraguay ( Page ) ; U. S. N.M. 

 Apical field without radii or circuli 2. 



2. Circuli very dense, largely transverse, wavy, broken and branching; 



weakly developed and very variable undulating transverse radii ; 

 scales transversely oval or nearly circular. These look like clupeid 



scales Bramocharax bransfordii Gill. 



Nicaragua (Bransford); U. S. N. M. 

 Circuli not very dense; apical field with evident growth-lines; no 



trace of radii anywhere 3. 



?). Scales small, transversely short-oval . Rceboides guatemalensis Gthr. 

 Scales extremely broad, but of the same type 



Charax and Acanthocharax. 

 There are clearly indicated several tribes ; Characini (Charax, Acanth- 

 ocharax and Rvehoides), Salminini (Salminus), and Cynopotamini 

 (Cynopotamus). The Bramocharax, if correctly determined, rep- 

 resents another group. 

 CURIMATIN^. Curimatus magdalense has scales like those of C. spilurus 

 Gthr. 



CLUPEIDiE. 



Opisthonema libertate scales (mine evidently immature) do not differ 

 from those of 0. oglinurn, except in the absence of pitting. The first 

 transverse radius is complete, the second always interrupted. 



Opisthopterus dovii belongs to the Pristigasterinae. The five transverse 

 circuli and the hyaline apical field are as in the Clupeinse, but the few 

 radii in the basal field are directed obliquely basad, instead of being 

 transverse. There are fine irregular apical radii, poorly developed. The 

 apical margin is not dentate. 



SYNODONTID^. 



Synodus evermanni scales are like those of S. foetens, but smaller, with 

 the nucleus nearer the centre. Probably most of this difference is due 

 to immaturity. 



POECILIIDjE. 



Poecilia sphenops scales do not difler appreciably from those of P. butleri. 

 Xiphophorus helleri scales resemble in structure those of Pseudoxipho- 



