86 Field Columbian Museum — Zoology, Vol. V. 



nearly or quite reaching ventrals, 1% in head; ventrals to vent, i^ 

 in head ; base of anal equals the length of the head ; origin of adipose 

 fin over the last ray of the anal; caudal fin forked, the lobes equal; 

 least depth of caudal peduncle 2^ in head; lateral line complete, 

 nearly straight; gill rakers short, rather slender, about 17 on the first 

 gill arch; vertebrae 16 + 17=33. 



Color light olivaceous above, silvery below; a broad bluish silvery 

 band becoming darker posteriorly from upper edge of gill opening to 

 base of caudal fin ; an oblong black caudal spot extending on the mid- 

 dle rays of caudal fin; a dark humeral blotch. Length about 4 inches. 



This species is very abundant and variable. Specimens from the 

 Rio Nazas, the upper waters of the Rio Conchos and from the Rio 

 Panuco average a little deeper than those from the other localities. 

 Those found in streams where vegetation is the most abundant are 

 the darker in color. The females are full of eggs, indicating that 

 the spawning season is the latter part of May and early in June. 

 Eggs small, the diameter of each .035 inch. 



81. Tetragonopterus aeneus Giinther. 



Tetragonopterus ceneus Giinther, Proc. Zool. Soc. London, i860, 

 319; Oaxaca, Mexico: Giinther Cat., v, 326, 1864; Oaxaca: 

 Jordan & Evermann, Bull. 47, U. S. Nat. Mus., 1896, 333. 



Tetragonopterus oaxacanensis Bocourt, Ann. Sci. Nat. Zool., ix, 

 1868, 62; Oaxaca. 



Lowland streams south of the city of Vera Cruz and of the Rio 

 Balsas. (Otopa; Cordoba; Motzorongo; Refugio; El Hule; Obispo; 

 Perez; Sanborn; San Juan Evangelista; San Geronimo; Tehuantepec.) 

 Head 3^ to 4; depth 2^ to 3 ; D. 10; A. 24 to 27 ; scales 8 or 9,35 

 to 38-6. Body elongate, or rather deep, compressed; head short; 

 mouth small; in some of the larger specimens the outer cusps of the 

 upper teeth protrude through the skin of the upper lip; snout short, 

 blunt, 4 in head; eye 2% ; maxillary rather slender, its posterior por- 

 tion nearly vertical and about % diameter of the eye; no teeth on 

 maxillary; origin of the dorsal fin midway between tip of snout and 

 base of caudal, or slightly near the snout; longest dorsal ray slightly 

 longer than the head; tip of pectorals reaching ventrals; pectoral ii 

 in head; tips of ventrals not quite reaching anal; lateral line complete, 

 slightly decurved; caudal fin deeply forked. 



Color light olivaceous, a silvery band on sides, ending in an oblong 

 caudal spot extending on middle rays of the caudal fin ; this band 

 is darker in dark colored specimens; a black humeral spot with trace 

 of a second one behind it. Length about 4 inches. Streams south of 

 Cordoba and south of the Rio Balsas. 



