THE AMERICAN TETRAGONOPTERINAE. 261 



Specimens examined. 



This species is identical with Astyanax bimaculatus in apparently all char- 

 acters except the teeth. In A. bimaculatus the teeth of the inner series of the 

 premaxillary are convex behind; the denticles correspond to this convexity 

 and are, therefore, arranged in a curve. This cui've varies from a crescent to 

 U-shape in a specimen from PLracicaba. In A. orthodus the anterior and pos- 

 terior surfaces of the teeth are similar, the denticles being arranged in nearly a 

 straight line. These species differ, therefore, as Micralestes differs from Myletes. 



Head 4; depth 21; D. 11; A. 31-34 in Truando,^ usually 30 in Patia 

 Basin;* scales 7 or 8-37 to 41^-6 above ventrals, 8 above origin of anal; eye 

 3-3.3 in the head; interorbital 2^. 



Dorsal and ventral profiles equally curved, the ventral curve continuous, 

 the dorsal profile very slightly concave over the eyes; maxillary distinctly 

 longer than in a specimen of A. bimaculatus of the same size, longer than eye, 

 a little less than 3 in the head; maxillary with one to four teeth. Width of 

 cheeks equal to diameter of eye in the adult; limbs of preopercle forming about 

 a right angle. 



In the position of the dorsal, equidistant from tip of snout and base of 

 upper caudal rays, and the position of the ventrals the specimens agree exactly 

 with one of A. bimaculatus of equal size from Rio Grande do Sul. Pectorals 

 reaching to ventrals or a little fvuther; ventrals to or near to anal; anal basis 

 convex; margin of anal nearly straight; adipose well developed. Predorsal 

 line more fully scaled than in A. bimaculatus, the young frequently with a series 

 of scales; the median scales in the adult more or less deeply notched, and fre- 

 quently with a narrow margin bent over the ridge of the scales of one side. 



A longitudinal oval, humeral spot; caudal spot sometimes continued to 

 end of middle rays, usually confined to the scaled area at their base, some- 



1 To origin of the caudal. 

 ' Largest specimen. 



33L 32 33 34 

 5, -5-> HTi "I" 

 4 _2 4 SMI 



' -V', -^-, ¥-, Y-, -V in the Truando, V , tt. -^^- •» Barbacoas. 



