eigenmann: the FRESHWATER FISHES OF BRITISH GUIANA 255 



uuu. Teeth in both jaws obliquely truncate, directed obliquely 



forward toward a median point Leporinus. 



/(. Gill-membranes free from the isthmus and from each other. 

 w. Dorsal with fifteen rays. (Cr&imchince.) 



x. An adipose fin; mouth large, maxillary extending to 



below middle of eye. Crenuchus. 



xx. No adipose fin; mouth small, maxillary extending to 



below anterior margin of eye Poecilocharax. 



ww. Dorsal short. (Aphyocharacinoe.) 



y. Lateral line complete; maxillary with a few teeth. 



Odontostilbe. 

 yy. Lateral line incomplete. 



z. Caudal naked; teeth pointed, with a notch on each 



side Aphyocharax. 



zz. Caudal scaled Aphyodite. 



oo. Premaxillary with two or more series of notched teeth. (See .-1.) 

 A . Gill-membranes united, free from the isthmus. Dorsal entirely behind the ventrals, in part over the anal ; 

 teeth pluricuspid incisors, a single tooth in the front row of each premaxillary; mouth small. 

 (Iguanodectince.) 



B. Breast not compressed to an edge Iguanodectes. 



BB. Breast compressed to an edge Piabucus. 



A A. Gill-membranes free from each other and from the isthmus; opercle not prolonged. 



C. No predorsal spine. 



D. Preventral area with a median edge; pectorals small, placed low; anal basis nearly horizontal; 



mouth large, with canines. (Agoniatince.) Agoniates. 



DD. Preventral area rounded, sometimes very narrow. 



E. Lower jaw with a single series of teeth. {Tctragonopteriiue.) 

 F. Gill-rakers setiform. 



G. Caudal scaled; anal with a basal sheath of scales. 



//. Lateral line much decurvedin front Tetragonopterus. 



////. Lateral line not greatly decurved, scales entire. 



/. Lateral line complete; predorsal area with a median series of scales: five 

 teeth in the inner series of the premaxillary; second suborbital not 



completely covering the cheek Mcenkhausia. 



II. Lateral line incomplete; caudal lobes equal. 



J. Maxillary with teeth along its entire margin Pristella. 



/./. Maxillary with few or no teeth Hemigrammus. 



GG. Caudal naked. 



K. Preventral area with several series of normal scales. 



L. Lateral line incomplete. Maxillary border a simple curve; origin of anal 

 behind origin of dorsal; scales cycloid. 



M. Pectoral normal Hyphessobrycon. 



MM. Pectoral archaic, a fleshy lobe surrounded by a fringe of filaments. 



Dermatocheir. 

 LL. Lateral line complete. 



2V. Maxillary border meeting premaxillary border at a right angle, its 



