THE AMERICAN TETRAGONOPTERINAE. 105 
below; maxillary equal to distance from tip of snout to pupil, three in the head. 
Usually four, sometimes five teeth in the outer row of the premaxillary, the second 
and third close together, the third withdrawn from the line; five teeth in the 
second series; maxillary with two or three minute teeth. 
Four large teeth in the front of the lower jaw, minute ones on the sides. 
Gill-rakers 7 + 10, about one third the diameter of the eye. 
Seales closely imbricate, with several striae; caudal lobes scaled for rather 
more than half their length; anal with a sheath of a single series of scales in 
front; lateral line but little decurrent, the rows of scales above and below it 
parallel with it; a well-developed axillary scale. 
Origin of dorsal usually nearer tip of snout than base of caudal, its height 
three and a half in the length, its highest ray nearly three times as high as its 
penultimate; caudal widely forked, the lobes longer than the height of the 
dorsal; anal emarginate, its highest ray reaching to base of last ray but five, 
its origin considerably behind the vertical from the last dorsal ray, its base 
about three and a half in the length; pectorals reaching ventrals, ventrals to or 
nearly to anal; origin of the ventrals equidistant from tip of snout and base 
of last anal ray. 
No caudal spot; a very narrow silvery band overlying a dark line; a well- 
defined humeral spot of numerous chromatophores above the third, fourth, and 
fifth scales of the lateral line; numerous chromatophores on the upper half of 
the cheek and opercle; a dark line of varying intensity and width along the 
base of the anal; scales of the back margined with dusky; scales of the median 
line in front of and behind the dorsal dusky, or with a dusky margin and a dusky 
median spot. The color varies much in intensity with different localities. 
Those from Jatuarana, Villa Bella, I¢a are pale, those from Obidos are dark. 
In life the vertical fins of the Guiana specimens at least are more or less tinged 
with red. 
Anterior anal rays of the male with recurved hooklets. 
Vertebrae 13 + 17. 
Posterior air-bladder about equal to the eye in diameter, more than twice 
the length of the anterior bladder, about three times as long as the eye, blunt 
behind and bent down to near the origin of the anal. Alimentary canal about 
equal to the length without the caudal. Insect eaters. 
There is considerable variation in shape in the Guiana specimens enumer- 
ated. The specimens from Rockstone are deep and thin, depth about 2.75; 
those from Konawaruk and the Potaro are more elongate and heavier. In the 
Konawaruk specimens the depth is 3.75. 
