240 THE AMERICAN CHARACIDAE. 



8. AsTYANAX (PoECiLURicHTHYs) siTviMEXRicus Eigenmann. 

 Plate 41, fig. 1. 



Astyanax symmetricus Eigenmann, Bull. M. C. Z., 1908, 52, p. 95; Rept. Princeton univ. exped. 

 Patagonia, 1910, 3, p. 432. 



One specimen 20768 in part. Type. 74 mm. Tabatinga. Bom-get. 



Allied to A. asymmetricus, A. anterior and A. zonatus. Distinguished by 

 the absence of a hmneral spot and the nearly symmetrical caudal spot. Most 

 nearly like A. zonatus, from which it differs, among other things, by the stria- 

 tion of its scales. 



Head 2.66; depth 2.63; D. 11; A. 30; scales 8-48-6; eye 3; interorbital 

 2.66. 



Symmetrically elliptical to the caudal peduncle, compressed. Preventral 

 area rounded, without a continuous median series of scales; postventral area 

 keeled. Predorsal area narrow, completely scaled, but without a median series 

 of scales. 



Occipital process narrow, 4f in the distance from its base to the dorsal, 

 bordered by 4 scales on the sides. Frontal fontanel not much shorter than the 

 posterior exclusive of the occipital groove. Second interorbital leaving a naked 

 area which is widest below. Maxillary equal to the eye. Premaxillary with 

 four teeth in the front row, of which the third is shghtly withdrawn from the line; 

 five graduated teeth in the second row, their denticles arranged in a crescent; 

 maxillary with a single small tooth; low^er jaw with three large, multicuspid 

 graduate teeth and about eight small ones on the side. The first and second 

 of the lateral teeth may be 2-pointed, the rest are retrorse conical, grading 

 from in front back, the first abruptly smaller than the anterior teeth but larger 

 than the following ones. 



Gill-rakers 10 + 15, about one third the length of the eye. 



Scales cycloid, regularly imbricate, an interpolated row between the second 

 and third or third and fourth series below the lateral line, above the second fourth 

 of the anal. Lateral line but little decurved, the row of scales below it parallel 

 with it, each scale with 2-4 radiating striae; axillary scale well developed. 



Origin of dorsal equidistant from tip of snout and base of upper caudiSl lobe ; 

 the fin pointed, its highest ray about 4 in the length. Anal emarginate, its origin 

 and the base of the last dorsal ray equidistant from the snout. Ventrals just 



