312 Field Museum of Natural History — Zoology, Vol. X. 



larger specimen; origin of anal slightly behind origin of pectorals, the 

 longest rays but little shorter than eye and snout; pectorals of moderate 

 length, 1. 1 7 to 1.2 in head. 



Color grayish buff; sides with dark points, forming an indistinct 

 dark area at beginning of lateral line and an indefinite dark streak on 

 lateral line, and short bars below base of anal rays; fins unmarked. 



Of this species we have only 2 specimens and the largest one is with- 

 out a tail. The smallest one measures 150 mm. in total length. Both 

 are from Marrigante, below the head of tide water on the Rio Tuyra. 



We have at hand for comparison many specimens from more south- 

 em localities. Our uninjured specimen appears to differ somewhat 

 from all the others that have been examined in the apparently deeper 

 body, shorter anal fin and the compressed caudal filament, which is 

 considerably longer than half the anal. It is, therefore, probable that 

 our specimens represent a new variety or species, but our material is 

 too meagre to establish this fact. 



Habitat: Rio Tuyra south to the Rio de la Plata. 



37. Genus Sternarchus Bloch & Schneider. 



Sternarchus Bloch & Schneider, Syst. Ichthyol., 1801, 497, PI. 94 (type 



Gymnotus albifrons Linnaeus). 



Body elongate, compressed; head large, naked; snout short, not tubu- 

 lar; fontanels present; eyes without free orbital margin; mouth large, its 

 angle little if any in advance of eyes; teeth in patches on both jaws; 

 scales cycloid; lateral line complete; caudal fin present, distinct; anal fin 

 long, but not reaching caudal fin, its origin at or a little in advance of 

 vertical from gill-opening. 



53. Sternarchus rostratus Meek & Hildebrand. 



Sternarchus rostratus Meek & Hildebrand, Field Mus. Nat. Hist. Pub., 



Zool. Ser., X, 1913, 85 (Rio Grande near Cana). 



Head 6.7 in length to base of caudal; depth 8.25. 



Body compressed throughout; head rather low, its greatest depth 

 1.8 in its length, its upper profile slightly concave; snout not greatly 

 produced, blunt, very slightly compressed, its length somewhat greater 

 than distance from anterior margin of eye to upper angle of gill- 

 opening, 2.3 in head; eye 18.5; interorbital 5.6; mouth rather large, its 

 angle under about middle of eye; upper jaw a little in advance of the 

 lower; gill-opening a small slit in advance of pectorals; lateral line com- 

 plete; mucus pores numerous and distinct on back and sides; vent 

 under margin of preopercle; dorsal filament present; caudal fin distinct, 



