100 THE AMERICAN CHARACIDAE. 



Predorsal area obscurely keeled, a median series of scales may extend from the 

 dorsal to the occipital process or a variable number of the median scales near 

 the occipital process may be divided into two halves, leaving a naked line con- 

 tinued from the occipital process; the median series of scales thus varies from 

 six to nine. 



Occipital process moderate, four or five times in the distance from its base 

 to the dorsal, bordered by three scales on the side. Interorbital convex; second 

 suborbital covering a variable amount of the cheeks but always leaving a com- 

 paratively broad naked border even in the large specimens (20722) ; maxillary 

 not reaching to the end of the first suborbital, equal to the length of the snout 

 or a little more. Premaxillary usually with four teeth in the front series, the 

 second tooth withdrawn from the line; rarely three or five teeth (in one case 

 six) in the front row, second row with five graduated teeth; maxillary usually 

 with one, rarely with two teeth; lower jaw with four, large graduated teeth on 

 each side and a number of smaller ones. 



Gill-rakers very small, about 6 + 9, longest about four in the diameter of 

 the eye. 



Scales regularly imbricate, thin, those on the sides with two to ten striae. 

 Anal naked, or its sheath composed of a single series of scales; caudal lobes 

 scaled for at least half their length; lateral fine very slightly decurved; four 

 scales between the origin of the anal and the lateral line; axillary scale well 

 developed. 



Origin of dorsal little nearer tip of snout than base of caudal; origin of ven- 

 trals scarcely nearer tip of snout than the dorsal; highest dorsal ray three and 

 a half in the length; anal emarginate, its origin below the first or second scale 

 behind the dorsal; ventrals about reaching anal or but little beyond anus, pecto- 

 rals nearly or quite to ventrals. 



Upper half of caudal, except a semicircular spot at the upper part of its 

 base, black of varying intensity, sometimes shading into light at the upper 

 margin and with the tip light; lower half of the caudal hyaline or dusky toward 

 the tip (20730) shading into the black of the upper lobe at the middle; a small, 

 horizontally oval, or round humeral spot over the second and third scales of 

 the lateral line; a silvery lateral band one fourth the diameter of the eye in 

 width, bordered above by dusky; iridescent steel-blue above, brassy below. 

 In the young the caudal markings are very faint. 



In living specimens from Guiana the base of the upper caudal lobe is con- 

 spicuous!}' yellow or orange or cherry, base of lower caudal lobe, adipose, dorsal 



