48 FIELD COLUMBIAN MUSEUM ZOOLOGY, VOL. V. 



17. Hyboffiuithus Agassiz. 

 THE SILVERY MINNOWS. 



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

 Hybognathus nuchalis Agassiz.)* 



Dionda Girard, Proc. Acad. Nat. Sci. Phila., 1856, 177. (Type, 

 Dionda episcopa Girard.) 



Algoma Girard, 1. c., 180. (Type, Algoma amara 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 OF HYBOGNATHUS. 



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



defined lateral band; eye small, 3^ in head episcopus 48 



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

 fined lateral band and a distinct caudal spot; 

 eye large, 2^ to 3 in head rasconis 50 



40. Hybognathus episcopus (Girard). SILVERY MINNOW. 



Dionda episcopa Girard, P.roc. Acad. Nat. Sci. Phila., 1856, 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, 1859; 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 amara Girard, Proc. Acad. Nat. Sci. Phila., 1856, 180; 



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



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

 Algoma fluviatilis 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 amara Jordan, Bull. U. S. Geol. Sur., 1876, 401; Browns- 

 ville, Texas. 



Hybognathus serenus Jordan, Bull. Geol. Sur., 1878, 401; Browns- 

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



1896, 214. 



