228 THE AMERICAN CHARACIDAE. 



mandible with strong teeth in front, abruptly minute conical ones on the sides 

 or more gradually very small ones on the sides, without conical teeth in a second 

 series; teeth of second series of premaxillai'y equal or graduated, usually five in 

 number, fom- in a few species; crowns of premaxillary and mandibulary teeth 

 usually ridged and denticulate; maxillary with a few or no (0-10) teeth; caudal 

 naked; lateral line complete; gill-rakers setiform; no predorsal spine. Form 

 usually slender, depth more than two in the length, except in A. biniaculatus, 

 A. lacustris, and ^. alleni. 



There is considerable difference in the character of the teeth of the second 

 row of the premaxillary. In some of the larger species the back of each tooth 

 of the inner series is convex, the front hollowed, spoon-fashion, and the ciuved 

 free margin is serrate, the median point strongest; the teeth of the lower jaw 

 are the reverse of this and since the two series of teeth alternate with each other 

 they form a zigzag cutting edge as the jaws are closed. The lower teeth pass 

 behind the upper ones. In some species, probably in all the smaller species, 

 the hollow of the teeth is sometimes reduced so that the teeth become simple, 

 serrate incisors. 



As here understood Astyanax is stripped of the forms having a scaled caudal, 

 an incomplete lateral line, a coiijibination of four teeth in the inner row of the 

 premaxillary with a completely armed suborbital, and of those with the entire or 

 nearly entire edge of the maxillary denticulate, all of which have until recently 

 been associated with it under Tetragonopterus. It is divisible into a group 

 without a complete series of scales between the dorsal and the occipital process 

 which includes most of the deep-bodied, smaller scaled species (Poecilurichthys) 

 and into a group of slenderer, sometimes minute, usually larger scaled species 

 with a regular and complete series of scales between the occipital process and 

 the dorsal (Astyanax). 



Astyanax is one of the dominant genera of South America. At present 

 it is found from Patagonia to the United States (New Mexico) and from tide- 

 water to high up in the mountains. It is found on both slopes of the Cordilleras 

 from Ecuador to Mexico. Two species are more conspicuous than the others 

 on account of their wide distribution, A. bimaculatus from La Plata to Panama, 

 'and A. fasciatus from the Rio Negro, Patagonia to Mexico. 



Astijanax bimaculatus is represented by more or less distinct varieties in 

 different localities. Of special interest in the same respect is A. fasciatus. This 

 species, so widely distributed, is absent from the Parahyba where it is replaced 

 by a distinct species; it is also absent from other rivers where it has probably 



