THE AMERICAN TETRAGONOPTERINAE. 115 
This is the most slender of the species of the genus. 
Head 4.25; depth 3.75-4.24; D. 10 (counting everything). A. most often 
19', scales 5-35 to 38-37; eye 2.75 in the head, equal to the interorbital. 
Slender, elongated, very little compressed, the width being about half the 
depth; head blunt, the dorsal and ventral profiles equally arched, without depres- 
sions or humps; preventral area rounded; postventral area compressed, very 
narrowly rounded; predorsal area rounded, without trace of a keel, with a 
median series of 9-11 scales between the dorsal and occipital process. 
Occipital process very short, about one eighth of the distance from its 
base to the dorsal, bordered by two scales on the sides; frontal fontanel less 
than one third as long as the parietal; interorbital flattish; second suborbital 
covering the entire cheek, leaving no naked portion; mouth small, the lower 
jaw included; maxillary short, equal to snout, three and three fourths in head; 
lower jaw equals diameter of eye. Four or five (rarely six) teeth in the front 
row of the premaxillary, the second tooth withdrawn from the line of the others, 
or the first pushed forward; four teeth in the inner series; maxillary with two 
or three teeth; mandible with four large teeth in front continued on the sides 
in a series of graduated teeth, the fifth tooth not notably smaller than the fourth 
tooth. 
Gill-rakers about 5 + 9, very small, the longest one fifth of the diameter of 
the eye. 
Seales deeply imbricate, without striae; anal sheath composed of a single 
series of small scales; caudal lobes scaled for at least one third of their length, 
the scales caducous. A well-developed axillary scale; lateral line very little 
decurved, the series of scales above and below it parallel with it. 
Origin of dorsal equidistant from tip of snout and caudal; the highest ray 
one fifth of the length; adipose fin behind the vertical from the last anal ray; 
caudal lobes equal to the depth; anal origin behind the vertical from the last 
dorsal ray. Origin of ventrals equidistant from tip of snout and second scale 
in front of the dorsal or tip of last anal ray. Ventrals not reaching anal, the 
pectorals not reaching the ventrals. 
Highly iridescent, silvery; a silvery lateral band two thirds as wide as eye, 
from humeral spot to caudal; a vertical humeral spot crossing the third and 
part of the fourth scale of the lateral line; a few pigment-cells on upper part 
of opercle and preopercle. Fins all hyaline, without chromatophores. 
1In eleven of the largest, three have eighteen, five nineteen, two twenty, and one has twenty-one rays. 
2 Of ten one has 5.5 seales above the lateral line, and one has 3.5 below it; one has thirty-five, two 
thirty-six, four thirty-seven, and one thirty-eight pores in the lateral line. 
