258 MEMOIRS OP THE CARNEGIE MUSEUM 



v. Premaxillary with a canine at each end and a double row of teeth 

 between them; mandible with three or four canines in front; 

 the last one much the largest. Maxillary with a canine at its 

 upper end and pectinate teeth along its margin; clavicle notched, 

 the lower angle of the notch produced, scale-Uke; checks partly 



naked Acanthocharax. 



"f. Premaxillary teeth in a single series (rarely one or two teeth forming 

 a second series); no canines at the ends of the series, but the 

 anterior teeth graduated, the tliird tooth largest, canine-like; 

 upper angle of maxillary without a canine, the teeth graduated 

 in both directions fi'om about the fifth tooth. Anterior teeth 

 of the lower jaw canines, of which the first i.s large, the second 

 very small, the teeth from the second to the sixth graduated, 

 the sixth being about the size of the first; first teeth of the pre- 

 maxillary graduated, the third tooth being the largest; clavicle 



not notched Heterocharax. 



vv- Teeth on palate; snout prolonged; body long, cylindrical or subcyUndrical. 



?. Snout moderate; some of the teeth canines; anal long. {Acestrorhamphirm.) 

 Maxillary with two canines, sUpping under the preorliital for its entire 



length Acestrorhynchus. 



JJ. Snout very long, slender, with small, conical teeth; anal short. Lepisosteus- 

 liko. ( Hydrocynince.) A single series of teeth in each jaw. Hydrocynus. 

 ii. Caudal rounded ; mouth large, teeth conical, some of them canines. No fontanels ; no adipose dorsal. 

 (Erythrininm.) 



0. Walls of the air-bladder normal; maxillary with a canine anteriorly Hoplias. 



00. Walls of the anterior portion of the air-bladder cellular; maxillary without a canine. 



X. Pterygoids with teeth; dorsal rounded Hoplerythrinus. 



Tw. Pterygoids without teeth; dorsal fin angular or pointed Erythrinus. 



Subfamily Bivibranchiin^. 

 BiviBRANCHiA gen. nov. 



Mouth minute, with a row of movable multicuspid teeth in the fleshy upper 

 lip, none in the lower lip; upper jaw pointed, freely protractile; nares separated 

 by a flap only; gill-membranes narrowly joined to the isthmus at a point below the 

 posterior margin of the eye; gills highly modified; gill-rakers on the anterior face 

 of the anterior arch fleshy, dendritic, a shorter papilliform series on its posterior 

 face, interlocking with the anterior rakers of the second arch; similar interlocking 

 rakers between subsequent arches; broad lamellae extending inward as the gill- 

 filaments extend outward on each arch, the lamellse with papillated ridges corre- 

 sponding to the rakers, so that the ridges of succeeding lamellse interlock. 



Scales firm, cycloid. Lateral line complete, scarcely decurved; fins naked; 

 anal very small; middle caudal rays with broad membranes; vertebrae 17 + 18 



