96 THE AMERICAN CHARACIDAE. 



anal rays. Distinguished by the oblique mouth, feeble dentition, rounded 

 anterior margin of the maxillary, and color of the caudal. 



Head about 4; depth usually 3, ranging from 2.75 to 3.5; D. 11; A. 25-28 '; 

 scales 5 or 5.5-34 to 39 2 -3 or 3.5 (to ventrals). Eye 2.4-2.6 in the head; inter- 

 orbital slightly less than eye. 



Elongate, moderately compressed; dorsal and ventral profiles nearly sym- 

 metrical, the ventral profile slightly more convex than the dorsal which is slightly 

 depressed over the head; preventral area rounded with obscure keels on the sides, 

 postventral area very narrowly rounded or keeled; predorsal area keeled, with a 

 median series of about ten scales from the occiput to the dorsal. 



Occipital process one fifth the distance from its base to the dorsal, bordered 

 by three scales on the sides; interorbital distinctly and evenly convex; second 

 suborbital variable, leaving a narrow naked area on the cheek; maxillary about 

 three in the head, equal to the distance from the tip of the snout to the pupil, 

 its anterior margin regularly arched; mandible two and a half in the head, very 

 oblique; mouth small, dentition feeble, usually four (3-5) teeth in the front 

 row of the premaxillary, the third removed slightly from the line of the others; 

 five, rarely six teeth in the inner series; maxillary without teeth or with one, 

 rarely two, feeble ones; lower jaw with four larger teeth and several minute 

 ones on the sides, the mouth is much smaller (narrower) and the dentition much 

 feebler than in M. lepidura of the same size. 



Gill-rakers long and slender, much longer than M. lepidura, about 11 + 16, 

 those of the upper arch similar to but shorter than those of the lower, the longest 

 one third to half the length of eye. 



Scales nearly semicircular, deeply imbricate, with several diverging striae 3 ; 

 anal sheath of a single series of scales; caudal lobes scaled for two thirds of their 

 length; a well-developed axillary scale. 



Dorsal about equidistant from tip of snout and base of caudal, its height 

 three and a half in the length; ventrals nearer tip of snout than the dorsal, 

 about equidistant from tip of snout and end of anal; origin of anal behind 



1 In twenty specimens from the Amazon Basin, six have twenty-five, seven twenty-six, five twenty- 

 seven, and two twenty-eight rays. 



2 In sixteen specimens from the Amazon Basin one has thirty-four, two have thirty-five, seven thirty- 

 six, and six thirty-seven pores in the lateral line. A specimen from Paraguay has thirty-nine; of fifteen 

 specimens from the Essequibo, six have thirty-six, eight thirty-seven, and one has thirty-nine. 



3 The striae usually start from about the same vertical line and diverge backward, one specimen 

 from Villa Bella (20711) and two from Jose-Fernandez (21006) differ from the rest. The condition 

 approaches that of M. grandisquamis. Successive pairs of striae are joined at the base and follow each 

 other like a series of stacked v's placed horizontally. The specimen from Jos6-Fernandez have the 

 depth 2.75 in the length. 



