120 FISHES OF WESTERN SOUTH AMERICA 
of the latter; opercular aperture small, low, and equal to interorbital space, mar- 
gined by a broad flap; mouth moderate, its gape slightly less than half the greatest 
width of head; a bulbous tympanum arises lateral to dorsal plate on each side, its 
length equal to internarial space. 
Paired fins short and horizontal; adipose very fleshy, short, elevated more than 
twice its length, its elevation 1.6 in the interorbital space, notched strongly into 
dorsal contour; D. I, 5, nearly 2 in the interorbital space, its longest ray equal to 
the interorbital plus the diameter of the orbit, its spine roughened along the ante- 
rior border; P. I, 6, spine broad and flat, 1.16 in length of head to end of opercle, 
about 32 low, antrorse hooks on forward border, about 24 longer retrorse hooks on 
posterior border; V. much smaller, broad, its longest rays about equal to interorbital 
space; A. long, low, fleshy, its length equal to that of the head; humeral process 
long, pointed, and equal to interorbital space; C. rounded, its upper rays the long- 
est, giving the fin an oblique form. 
Color light or medium brown, on back and sides, above; lower lateral aspect 
and belly with yellow ground-color, and diffuse, scattered spots; numerous brown- 
ish chromatophores more or less grouped in patches; caudal with a diffuse band of 
brown describing an obliquely vertical arc midway of its rays. 
A thick coating of mucus over the entire fish. 
67. TRACHYCORYSTES ISACANTHUS (Cope) 
Auchenipterus isacanthus Cope, 1878, Proc. Amer. Phil. Soc., XVII, 677. 
Trachycorystes isacanthus Eigenmann and Kigenmann, 1888, Proc. Cal. Acad. Sci., (2), I, 154; 
Eigenmann and Eigenmann, 1890, Occ. Papers Cal. Acad. Sci. I, 275; 
Figenmann, 1910, Rept. Princeton Univ. Exped. Patagonia, III, 396. 
Known only from the Maranon. 
68. TRACHYCORYSTES BREVIBARBUS (Cope) 
Auchenipterus brevibarbus Cope, 1878, Proc. Amer. Phil. Soc., XVII, 676. 
Trachycorystes brevibarbus Eigenmann and Eigenmann, 1888, Proc. Cal. Acad. Sci., (2), I, 155; 
Eigenmann and Eigenmann, 1890, Occ. Papers Cal. Acad. Sci., I, 279; 
Eigenmann, 1910, Rept. Princeton Univ. Exped. Patagonia, IIT, 396. 
Known only from Cope’s material from the Maranon. 
69. TRACHYCORYSTES CORACOIDEUS Eigenmann and Allen, sp. nov. 
15794, 3, 128-136 mm., Iquitos, Morris, 1922. 
Head broad, its width less than the length; snout broad, the jaws of equal 
length; eye large, longer than the snout, about 3 in the interorbital, 4 in the length 
of the head to end of opercle; pit of fontanel long, the fontanel much shorter, sepa- 
rated by a bridge from the anterior pit; head granular, the occipital process broad ; 
the dorsal plate with a descending process behind; humeral process extending to 
below the downward process of the dorsal plate, nearly horizontal; maxillary barbel 
