THE AMERICAN TETRAGONOPTERINAE. 129 
parietal fontanel somewhat wider than the frontal, extending as a groove to the 
tip of the short occipital process; surface of bridge between the fontanels 
below the surface of the skull; interorbital slightly convex; cheeks nearly 
covered, the naked area between the second suborbital and the preopercle only 
about one fifth the width of the third preorbital; a notch between the first 
suborbital and preorbital, the maxillary slipping under the preorbital but not 
under the first suborbital; premaxillary-maxillary border angulated, the 
maxillary reaching but little beyond anterior border of eye. 
Mouth and dentition as in Tetragonopterus; the lower jaw with four 
heavy teeth on each side, abruptly followed on the side by minute teeth; pre- 
maxillary with three or four teeth on the front series, one of which frequently 
drops out of line; five graduated, multicuspid incisors in the inner series; the 
tips of the cusps very unequal in height, arranged in a nearly straight line. 
Maxillary without teeth. 
Gill-membranes free from the isthmus, gill-rakers 7 + 15, slender, about 
one half as long as the filaments. 
Seales with the margin slightly crenate, the exposed part of the scale 
with numerous slightly diverging striae; lateral line reaching to above ventrals; 
anal with a sheath; caudal partly sealed, ventrals with a slender axillary scale; 
lateral line scarcely decurved. 
Fins with exception of caudal all small; the origin of the dorsal in the 
middle of the body, very little behind the ventrals; adipose fin over end of 
the small, emarginate anal. Pectoral about equal to head less opercle, not 
reaching to ventrals; ventrals a little nearer tip of snout than dorsal, slightly 
shorter than pectoral, not reaching anal; anus nearer ventrals than anal; anal 
emarginate, its highest (first and second divided) rays reaching at least to base 
of the last, sometimes to the tip of the last rays; last ray not reaching more 
than halfway to caudal; dorsal small, its height equals length of head less 
half the opercle; caudal large, forked at the middle, the lower lobe much the 
longer, equals distance from tip of snout to middle of pectoral. 
Brassy; anterior anal lobe usually dusky; male with a black band from 
upper angle of gill-opening to base of middle caudal rays, then obliquely along 
the upper part of the lower caudal lobe; female with a similar band on the 
caudal: the band on the sides extending obliquely upward to the first row of 
seales below the origin of the dorsal which is the second row above the dark 
stripe of the male. 
Posterior part of air-bladder about twice as long as the anterior, scarcely 
