48 Field Columbian Museum — Zoology, Vol. V. 



17. Hybognathus Agassiz. 

 The Silvery Minnows. 



Hybognathus Agassiz, Anier. Jour. Sci. Arts, 1855, 223. (Type, 

 Hybognathus nuchalis Agassiz.) 



Dionda Girard, Proc. Acad. Nat. Sci. Phila., 1S56, 177. (Type, 

 Dion da episcopa Girard.) 



Algoma Girard, 1. c, 180. (Type, Algoma aniara Girard.) 



Body elongate, somewhat compressed; mouth small, horizontal 

 or oblique; the jaws normal, sharp-edged; lower jaw with a slight, 

 hard protuberance on anterior margin; no barbel; upper jaw pro- 

 tractile; teeth 4-4, with grinding surface, little if any hooked; alimen- 

 tary canal elongate, three or more times length of body; peritoneum 

 black; scales large, about 40 in lateral series; dorsal fin in advance 

 of ventrals; anal fin short. Small fishes usually inhabiting streams 

 with considerable current. 



KEY TO THE SPECIES OE HYBOGNATHUS. 



a. Body robust, depth less than 4 in body; no well page 



defined lateral band; eye small, 3 % in head cpiscopns 48 



aa. Body rather slender, depth 4 in body ; a well de- 

 fined lateral band and a distinct caudal spot; 

 eye large, 2 ~ 3 to 3 in head rascouis 50 



40. Hybognathus episcopus (Girard). Silvery Minnow. 



Dionda episcopa Girard, Proc. Acad. Nat. Sci. Phila., 1S56, 177; 



Comanche Spring, a tributary of the Rio Grande. 

 Dionda melanops Girard, Proc. Acad. Nat. Sci. Phila., 1856, 178; 



Buena Vista, Coahuila: Girard, Mex. Bd. Sur., 44, pi. xxvi, 



figs. 17-20, 1S59; Buena Vista, Coahuila. 

 Dionda couchi Girard, Proc. Acad. Nat. Sci. Phila., 1856, 178; 



Guajuco, Monterey, and Cadereita, Nuevo Leon: Girard, Mex. 



Bd. Sur., 44, pi. xxvi, figs. 1-4, 1859; Guajuco, Monterey and 



Cadereita, Nuevo Leon. 

 Algoma aniara Girard, Proc. Acad. Nat. Sci. Phila., 1S56, 180; 



Lagoon near Ft. Brown, Texas: Girard, Mex. Bd. Sur., 45, pi. 



xxvii, figs. 17-20, 1859; Ft. Brown, Texas. 

 Algoma diiviatilis Girard, Proc. Acad. Nat. Sci. Phila., 1856, 181; 



near Monterey, Nuevo Leon: Girard, Mex. Bd. Sur., 45, pi. 



xxvii, figs. 17-20, 1859; Monterey, Nuevo Leon. 

 Dionda aniara Jordan, Bull. U. S. Geol. Sur., 1876, 401; Browns- 

 ville, Texas. 

 Hybognathus serenus Jordan, Bull. Geol. Sur., 1S78, 401; Browns- 

 ville, Texas: Jordan & Evermann, Bull. 47, U. S. Nat. Mus., 



1 896, 214. 



