FAMILY VI. CHARACINID^E. 85 



The species of this genus, which inhabit the streams of Mexico, 

 are extremely variable. In the collections studied by me, I am 

 unable to recognize more than two species. 



KEY TO THE SPECIES OF TETRAGONOPTERUS. 



a. Anal fin short, its rays 18 to 23 mexicanus 85 



aa. Anal fin longer, its rays 24 to 27 aneus 86 



80. Tetragonopterus mexicanus Filippi. 



Tetragonopterus mexicanus Filippi, Guerins Rev. Mag. Zool., 1853, 

 1 66; Mexico: Jordan & Evermann, Bull. 47, U. S. Nat. Mus., 

 1896, 335: Jordan & Snyder, Bull. U. S. Fish Comm., 1900, 

 125; Rio Ixtla, Puente de Ixtla, Morelos: Meek, Field Col. 

 Mus. Pub. 65, 1902, 86; Puente de Ixtla; Balsas; Cuicatlan; 

 Venta Salada. 



Astyanax argentatus Baird & Girard, Proc. Acad. Nat. Sci. Phila., 

 1854, 27; Comanche Spring and Brownsville, Texas: Girard, 

 Mex. Bd. Sur., 74, pi. vin, figs. 5-9, 1859; mouth of the Rio 

 Grande: Giinther, Cat., v, 380, 1864: Garman, Bull. Mus. 

 Comp. Zool., 1881, 92; tributaries of Lago del Muerto and 

 spring near Monclova. 



Tetragonopterus fulgens Bocourt, Ann. Sci. Nat. Zool., ix, 1868, 

 62; Province of Cuernavaca: Vaillant & Pellegrin, Bull. Mus. 

 Hist. Nat. Paris, 1904, 325; Cuernavaca. 



Tetragonopterus argentatus Woolman, Bull. U. S. Fish Comm., 

 1894, 60; Rio Chihuahua, Chihuahua: Jordan & Evermann, 

 Bull. 47, U. S. Nat. Mus., 1896: Jordan & Snyder, Bull. U. S. 

 Fish Comm., 1900, 125; Rio Verde, near Rascon, San Luis 

 Potosi; Rio Tamesin, Tampico: Meek, Field Col. Mus. Pub. 

 65, 1902, 86; Chihuahua; Santa Rosalia; Jimenez. 

 Tetragonopterus nitidus Vaillant & Pellegrin, Bull. Mus. Hist. Nat. 



Paris, 1904, 324; Cuernavaca. 



Rio Balsas and Rio Tehuacan to the Rio Grande. (Lerdo ; Santiago 

 Papasquiaro; Monterey; San Juan; Montemorelos ; Linares; Garza 

 Valdez ; La Cruz ; Santa Engracia ; Victoria ; Rio Verde ; Forlon ; Valles 

 Rascon; Cuautla; Yautepec; Jojutla; Atlixco; Matamoras; Chietla.) 



Head 3^ to 4; depth 2%" to 3; D. 9 or 10; A. 20 to 23; scales 

 8-34 to 37-6. Body elongate, compressed, the dorsal and ventral 

 outlines similar; head rather small; snout bluntish; mouth terminal, 

 small ; the free straight portion of the maxillary 3 X m head ; snout 

 3 to 3^; eye 3 to 3^! origin of dorsal fin about midway between 

 tip of snout and base of caudal fin (in most specimens nearer tip of 

 snout); base of dorsal i> in its longest ray, 2 in head; pectorals 



