84 FIELD COLUMBIAN MUSEUM ZOOLOGY, VOL. V. 



maxillaries protractile; teeth various, often incisor-like, often wanting; 

 branchiostegals usually 3; gill membranes united to the isthmus or 

 not; no pseudobranchiae; gills 4, a slit behind the fourth; lower 

 pharyngeals more or less curved, armed with small, sometimes villi- 

 form, teeth ; adipose fin present (occasionally wanting) ; air bladder 

 transversely divided into two portions; anterior vertebrae coalesced 

 and modified. 



A large family of fishes inhabiting the fresh waters of South 

 America and Africa. A few species inhabit the streams of southern 

 Mexico, ranging as far north as the United States. All of the mem- 

 bers of this family in Mexico are small, none reaching a length of 

 over six inches. 



KEY TO THE GENERA OF CHARACINID/E. 



a. Scales large, less than 50 in the lateral series; PAGE 



anal fin short, with less than 35 rays, 

 b. Anterior teeth strong, incisor-like; premax- 

 ' illary teeth in a double series, those on man- 

 dible in a single series; less than 40 scales 

 in the lateral series ; lateral line complete . . Tetragonopterus 84 

 bb. Anterior teeth weaker, more or less conical 

 and with lateral cusps; more than 40 scales 

 in the lateral series; lateral line incomplete. Hemigrammus 87 

 aa. Scales small, more than 60 in the lateral series; 



anal fin long, with more than 40 rays Rceboides 88 



Subfamily Tetragonopterinae. 

 35. Tetragonopterus Cuvier. 



Tetragonopterus Cuvier, Regne Animal, Ed. i, Vol. n, 166, 1817. 

 (Type, Tetragonopterus argenteus Cuvier.) 



Astyanax Baird & Girard, Proc. Acad. Nat. Sci. Phila., 1854, 26. 

 (Type, Astyanax argentatus Baird & fiirard.) 



Body oblong or elevated, compressed, covered with moderate 

 scales; belly rounded; mouth rather small; anterior teeth strong, 

 incisor-like; lateral teeth small; premaxillary and mandibular teeth 

 about equal in size, with a compressed, notched crown, the former 

 in a double, the latter in a single series; nostrils of each side close 

 together, separated by a valve only; lower pharyngeals very slender, 

 curved, armed with a single series of slender, hooked teeth; gill 

 openings wide; gill membranes not connected, free from the isthmus; 

 origin of the dorsal fin about midway between tip of snout and base 

 of caudal. 



