12 Annals of the Carnegie Museum. 



opercle ; teeth in bands of about four irregular series ; origin of anal 

 under middle of dorsal ; dorsal fulcra extending forward to near the 

 dorsal ; caudal rounded ; first pectoral ray prolonged in a filament 

 nearly as long as the rest of the ray ; everywhere except on belly and 

 lower surface of head with round dark spots ; caudal dusky, the mar- 

 gin light. 



In the cotypes the head is comparatively longer, 5 in the length ; 

 the color is light below, uniformly yellowish brown above ; pectoral 



filament short. 



Order PLECTOSPONDYLI. 



Family CHARACID^.. 



Subfamily GASTEROPELICINLE. 



The genera of Gasteropelicinae are very similar. They differ from 



each other in dentition and the development of the adipose fin. They 



may be distinguished among themselves by the characters indicated in 



the following key : 



a. No adipose fin ; maxillary with a single large tooth ; premaxillary teeth in a single 

 series. Camegiella Eigenmann. 



aa. Adipose dorsal present. 



b. Maxillary with large conical or hooked teeth. 



c. Premaxillary teeth in two series. Thoracocharax Fowler. 



cc. Premaxillary teeth in a single series. Gasteropelecus Linnaeus. 



bb. Maxillary without teeth ; premaxillary teeth in a single or double series. 



Pterodiscus 1 Eigenmann. 



2 Pterodiscus gen . nov. 

 Type : Pterodiscus levis sp. nov. 



Characters of Gasteropelecus, but the maxillary without teeth, and the premaxillary 

 teeth in one or two series. 



Pterodiscus levis sp. nov. 



Type, 47 mm., No. 54454 U. S. Nat. Mus., Para. J. C. Brevoort. 



Cotypes, 37 and 46 mm., No. 34454 U. S. Nat. Mus., and 32 mm. (to base of 

 caudal), No. 11479 I. U. Mus., Para. J. C. Brevoort. 



Head 4-4.25 ; depth 1.8; D. 10 or II ; A. 31, 31, 35 and 32 respectively ; lat. 1. 

 18 ; 29-32 scales in a median lateral series ; eye 3 in the head, 1. 5 in the interorbital. 



No teeth on the maxillary. 'Premaxillary teeth in a single series in two specimens, 

 one tooth moved forward forming an additional series in the two other specimens. 



A dark lateral streak ; base of anal and margin of disk dark. 



I am not able to detect material differences between the specimens of this species, 

 all old and poor, and typical Gasteropelecus sternicla except in the absence of teeth on 

 the maxillary. 



