412 A Revision of the 



Compressed. Pre ventral region flat or slightly concave, with blunt 

 lateral keels; post ventral region strongly compressed, with a series of 

 spiniform scales. Median line before dorsal naked; postdorsal region 

 rounded. Scales small, all very strongly ctenoid. 



Head depressed above the eyes; eye about equal to snout, 2 in the 

 interorbital. 



Origin of dorsal about an orbital diameter nearer to tip of snout than 

 to base of upper caudal rays. Caudal rays much branched. Anal 

 emarginate; pectorals reaching past the origin of ventrals. 



Air-bladder extending beyond origin of anal. 



Yellowish, with brassy reflections; a black spot at end of lateral line. 



Head 3^-3^; depth 2^-2^; D. 12-13; A. 16-17. Lat. 1. 94-103. 



3. PSECTR004STER gen. iiov. 



Type, Psectrogaster rhomboides sp. nov. 



Teeth none. Lateral line developed. Postventral region trenchant, 

 the scales of each side with a narrow margin bent over the ventral ridge 

 and terminating medially in a spiniform process. Preventral region 

 rounded; predorsal region entirely scaled. Scales 50-60. 



This genus is closely related to Potamorhina, from which it differs in 

 having much larger scales, etc. 



Analysis of the species: — 



a. Air-bladder extending to origin of anal. Origin of dorsal about 



equidistant between tip of snout and base of upper caudal 



fulcra. Origin of ventrals nearer to base of caudal than to 



tip of snout. Scales 15-55-10. 7'homboides, 1. 



aa. Air-bladder extending to posterior end of anal. Origin of dorsal 



about equidistant from tip of snout and from tip of adipose 



fin. 



b. Depth $ and ? about 2^. Lat. 1. 49-56. amazonica, 2. 



bb. Depth ? 2^. Scales 56. Profile convex. ciliatus, 3. 



1. PSECTRO&ASTEiR RHOMBOIDES 8p. nov. 



Curimatus cyprinoides Steind., '81a, 34 (RioPuty),notof L., Gthr., et al. 



Types, No. 20303, 20304, 20306, over fifty specimens, Rio Puty; O. 

 St. John. 



No. 20310, one specimen, San Gon9allo; O. St. John. 



Compressed rhomboidal, the dorsal and ventral outlines making an- 

 gles at the origin of the dorsal and of the ventral fins. Preventral re- 

 gion rounded. Postventral region trenchant, without a median series 

 of scales. The scales of each side with a narrow margin bent over the 

 ventral ridge and terminating medially in a spiniform process. Back 

 narrow, without keels. 



Profile more or less depressed at the occiput. Eye with a narrow 

 anterior and posterior adipose lid, about 1 in snout, 3^-4 in head, lf-2 

 in interorbital. , 



