THE AMERICAN TETRAGONOPTERINAE. 



99 



The species is very variable in shape, number of anal rays and scales. It 

 is distinguished by the peculiar coloration of the upper half of the caudal. 



Head 3.75-L4; depth 3 2 -3.5; D. 11; A. most often 24, ranging from 22- 

 27 3 ; scales 5-35-4 4 . Eye 2.5-3, about equal to the interorbital. 



Elongate, moderately compressed, greatest depth under origin of dorsal, 

 the dorsal and ventral profiles evenly curved, or the ventral profile more arched, 

 or preventral area broadly rounded; postventral area very narrowly rounded. 



1 In part. 



2 In some of the specimens (20788) from Santarem, and some of those from Guiana, the depth is 

 much greater, 2.75 in the length. 



3 Of fifty-five specimens six have twenty-two anal rays, sixteen twenty-three, twenty-one, twenty- 

 four, seven twenty-five, two twenty-six, and three twenty-seven. 



4 In one case there were found six scales above the lateral line, in two cases five and one half. The 

 scales along the lateral line average thirty-five, but range from thirty-one to thirty-seven. In twenty- 

 four one has thirty-one scales, five thirty-four, eleven thirty-five, five thirty-six, and two thirty-seven. 



