THE AMERICAN TETRAGONOPTERINAE. 279 



1 in the snout, 4 in the head; A. 27; maxillary with one tooth; dorsal and anal 

 profile about equally (?) arched; second preorbital striate; a large, oval humeral 

 spot, twice as long as high; a dark caudal spot extending forward on the sides; 

 trace of longitudinal streaks between the rows of scales. 



34. AsTYANAX MUCRONATUS Eigeumami. 

 Plate 53, fig. 1. 



Ashja7mx mucronalus Eigenmann, Ann. Carnegie mus., 1909, 6, p. 19; Repts. Princeton, univ. exped. 

 Patagonia, 1910, 3, p. 433; Mem. Carnegie mus., 1912, 5, p. 354, pi. 51, fig. 4. 



Habitat. — Lower Potaro River, Guiana. 



Specimens examined. 

 Catalogue iNTumber of Size 



number specimens in mm. Locality CoUector 



1025 C. Tj-pe 1 53 Tumatuniari above the Falls Eigenmann 



1026 C, 11725 I. Paratypes 3 51-54 Tumatuniari above the Falls Eigenmann 



1027 C, 11726 1. Paratypes 14 46-73 Potaro at Tukeit Eigenmann 



Head 3.6; depth 2.3-2.6; D. 11; A. 25-26, rarely 27; scales 6.-34 or 35-5 

 (rarely 4); eye 2.7, 2 in the head without the opercle; interorbital 3-3.5 in the 

 head. 



Compressed, subrhomboidal, with heavy head and slender caudal peduncle. 

 Dorsal profile slightly depressed over the eye, rising with a gentle curve to the 

 origin of the dorsal, abruptly descending to the end of the dorsal and then with 

 a more gentle slope to the caudal peduncle. Ventral profile more regularly 

 arched. Preventral region broadly romided, postventral area more narrowly 

 rounded. Predorsal area keeled, with a median series of 8 scales. 



Occipital crest exceptionally narrow at the base, about one fom-th of the 

 distance from its base to the dorsal, bordered by 3 scales on the sides; skull 

 narrow, sUghtly convex, smooth. Fontanels very narrow and long, the frontal 

 fontanel as long as the parietal. Second suborbital leaving but a very narrow 

 naked area. Maxillary but little longer than snout, 3.3 in the head. Pre- 

 maxillary with two or three teeth in the front series, five teeth in the second 

 series, their denticles in a straight line; two teeth on the maxillary; lower jaw 

 with eight teeth arranged in a crescent four on each side, smaller teeth on the sides. 



Gill-rakers 5 + 10. 



Scales very regularly imbricate, without interpolated or omitted rows, each 

 scale with several, slightly diverging striae; anal sheath of a single row of scales 

 along the base of the anterior rays; caudal naked. 



